[yt-svn] commit/yt: 28 new changesets

commits-noreply at bitbucket.org commits-noreply at bitbucket.org
Thu Jun 18 06:17:37 PDT 2015


28 new commits in yt:

https://bitbucket.org/yt_analysis/yt/commits/7d409e929b96/
Changeset:   7d409e929b96
Branch:      yt
User:        jzuhone
Date:        2015-05-15 13:38:06+00:00
Summary:     Docstring should reflect the correct module name
Affected #:  1 file

diff -r 4b4b61882407d5a5c909647b24a0147f67eee5ac -r 7d409e929b9677b2fd99232163d6941911468a82 yt/analysis_modules/ppv_cube/tests/test_ppv.py
--- a/yt/analysis_modules/ppv_cube/tests/test_ppv.py
+++ b/yt/analysis_modules/ppv_cube/tests/test_ppv.py
@@ -1,5 +1,5 @@
 """
-Unit test the sunyaev_zeldovich analysis module.
+Unit test the PPVCube analysis module.
 """
 
 #-----------------------------------------------------------------------------


https://bitbucket.org/yt_analysis/yt/commits/8378ed9f4cdf/
Changeset:   8378ed9f4cdf
Branch:      yt
User:        jzuhone
Date:        2015-05-15 13:38:37+00:00
Summary:     Remove second return statement
Affected #:  1 file

diff -r 7d409e929b9677b2fd99232163d6941911468a82 -r 8378ed9f4cdff934c728b57c2da266f0b2b696d2 yt/visualization/volume_rendering/camera.py
--- a/yt/visualization/volume_rendering/camera.py
+++ b/yt/visualization/volume_rendering/camera.py
@@ -2252,7 +2252,6 @@
             def temp_weightfield(a, b):
                 tr = b[f].astype("float64") * b[w]
                 return b.apply_units(tr, a.units)
-                return tr
             return temp_weightfield
         ds.field_info.add_field(weightfield,
             function=_make_wf(field, weight))


https://bitbucket.org/yt_analysis/yt/commits/dbbc3defc965/
Changeset:   dbbc3defc965
Branch:      yt
User:        jzuhone
Date:        2015-05-15 13:51:29+00:00
Summary:     FITSImageBuffer --> FITSImageData. Fixing some small issues.
Affected #:  1 file

diff -r 8378ed9f4cdff934c728b57c2da266f0b2b696d2 -r dbbc3defc9655d675e02487a50a2a697755f1d6a yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -1,5 +1,5 @@
 """
-FITSImageBuffer Class
+FITSImageData Class
 """
 
 #-----------------------------------------------------------------------------
@@ -66,7 +66,7 @@
         >>> prj = ds.proj(2, "kT", weight_field="density")
         >>> frb = prj.to_frb((0.5, "Mpc"), 800)
         >>> # This example just uses the FRB and puts the coords in kpc.
-        >>> f_kpc = FITSImageBuffer(frb, fields="kT", units="kpc")
+        >>> f_kpc = FITSImageData(frb, fields="kT", units="kpc")
         >>> # This example specifies a specific WCS.
         >>> from astropy.wcs import WCS
         >>> w = WCS(naxis=self.dimensionality)
@@ -141,15 +141,15 @@
                 # FRBs are a special case where we have coordinate
                 # information, so we take advantage of this and
                 # construct the WCS object
-                dx = (img_data.bounds[1]-img_data.bounds[0]).in_units(units)/self.nx
-                dy = (img_data.bounds[3]-img_data.bounds[2]).in_units(units)/self.ny
-                xctr = 0.5*(img_data.bounds[1]+img_data.bounds[0]).in_units(units)
-                yctr = 0.5*(img_data.bounds[3]+img_data.bounds[2]).in_units(units)
+                dx = (img_data.bounds[1]-img_data.bounds[0]).in_units(units).v/self.shape[0]
+                dy = (img_data.bounds[3]-img_data.bounds[2]).in_units(units).v/self.shape[1]
+                xctr = 0.5*(img_data.bounds[1]+img_data.bounds[0]).in_units(units).v
+                yctr = 0.5*(img_data.bounds[3]+img_data.bounds[2]).in_units(units).v
                 center = [xctr, yctr]
                 cdelt = [dx,dy]
             elif isinstance(img_data, YTCoveringGridBase):
                 cdelt = img_data.dds.in_units(units).v
-                center = 0.5*(img_data.left_edge+img_data.right_edge).in_units(units)
+                center = 0.5*(img_data.left_edge+img_data.right_edge).in_units(units).v
             else:
                 # If img_data is just an array, we assume the center is the origin
                 # and use *pixel_scale* to determine the cell widths
@@ -209,22 +209,19 @@
 
     def to_glue(self, label="yt", data_collection=None):
         """
-        Takes the data in the FITSImageBuffer and exports it to
-        Glue (http://www.glueviz.org) for interactive
-        analysis. Optionally add a *label*. If you are already within
-        the Glue environment, you can pass a *data_collection* object,
-        otherwise Glue will be started.
+        Takes the data in the FITSImageData instance and exports it to
+        Glue (http://www.glueviz.org) for interactive analysis. Optionally 
+        add a *label*. If you are already within the Glue environment, you 
+        can pass a *data_collection* object, otherwise Glue will be started.
         """
         from glue.core import DataCollection, Data
         from glue.core.coordinates import coordinates_from_header
         from glue.qt.glue_application import GlueApplication
 
-        field_dict = dict((key,self[key].data) for key in self.keys())
-        
         image = Data(label=label)
         image.coords = coordinates_from_header(self.wcs.to_header())
-        for k,v in field_dict.items():
-            image.add_component(v, k)
+        for k,v in self.items():
+            image.add_component(v.v, k)
         if data_collection is None:
             dc = DataCollection([image])
             app = GlueApplication(dc)
@@ -365,12 +362,12 @@
 
 class FITSSlice(FITSImageBuffer):
     r"""
-    Generate a FITSImageBuffer of an on-axis slice.
+    Generate a FITSImageData of an on-axis slice.
 
     Parameters
     ----------
-    ds : FITSDataset
-        The FITS dataset object.
+    ds : :class:`yt.data_objects.api.Dataset`
+        The dataset object.
     axis : character or integer
         The axis of the slice. One of "x","y","z", or 0,1,2.
     fields : string or list of strings


https://bitbucket.org/yt_analysis/yt/commits/f165aa37acd5/
Changeset:   f165aa37acd5
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:13:38+00:00
Summary:     We won't subclass from HDUList anymore, so that we can implement __getitem__ to give back YTArrays. Instead, we will use HDUList under the hood and replicate some of its methods
Affected #:  1 file

diff -r dbbc3defc9655d675e02487a50a2a697755f1d6a -r f165aa37acd5f0b3e56f3b9aa2b9cfa6ce94d81b yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -126,17 +126,13 @@
                 hdu.header["btype"] = key
                 if hasattr(img_data[key], "units"):
                     hdu.header["bunit"] = re.sub('()', '', str(img_data[key].units))
-                self.append(hdu)
+                self.hdulist.append(hdu)
 
-        self.dimensionality = len(self[0].data.shape)
-        
-        if self.dimensionality == 2:
-            self.nx, self.ny = self[0].data.shape
-        elif self.dimensionality == 3:
-            self.nx, self.ny, self.nz = self[0].data.shape
+        self.shape = self.hdulist[0].shape
+        self.dimensionality = len(self.shape)
 
         if wcs is None:
-            w = pywcs.WCS(header=self[0].header, naxis=self.dimensionality)
+            w = pywcs.WCS(header=self.hdulist[0].header, naxis=self.dimensionality)
             if isinstance(img_data, FixedResolutionBuffer):
                 # FRBs are a special case where we have coordinate
                 # information, so we take advantage of this and
@@ -174,7 +170,7 @@
         """
         self.wcs = wcs
         h = self.wcs.to_header()
-        for img in self:
+        for img in self.hdulist:
             for k, v in h.items():
                 img.header[k] = v
 
@@ -186,26 +182,68 @@
         for img in self: img.header[key] = value
 
     def keys(self):
-        return [f.name.lower() for f in self]
+        return self.fields
+
+    def __getitem__(self, field):
+        if field not in self.keys():
+            raise KeyError("%s not an image!" % field)
+        idx = self.fields.index(field)
+        return YTArray(self.hdulist[idx].data, self.field_units[field])
 
     def has_key(self, key):
-        return key in self.keys()
+        return key in self.fields
 
     def values(self):
-        return [self[k] for k in self.keys()]
+        return [self[k] for k in self.fields]
 
     def items(self):
-        return [(k, self[k]) for k in self.keys()]
+        return [(k, self[k]) for k in self.fields]
 
-    def writeto(self, fileobj, **kwargs):
-        pyfits.HDUList(self).writeto(fileobj, **kwargs)
+    def get_header(self, field):
+        """
+        Get the FITS header for a specific field.
 
-    @property
-    def shape(self):
-        if self.dimensionality == 2:
-            return self.nx, self.ny
-        elif self.dimensionality == 3:
-            return self.nx, self.ny, self.nz
+        Parameters
+        ----------
+        field : string
+            The field for which to get the corresponding header. 
+        """
+        if field not in self.keys():
+            raise KeyError("%s not an image!" % field)
+        idx = self.fields.index(field)
+        return self.hdulist[idx].header
+
+    @parallel_root_only
+    def writeto(self, fileobj, fields=None, clobber=False, **kwargs):
+        r"""
+        Write all of the fields or a subset of them to a FITS file. 
+
+        Parameters
+        ----------
+        fileobj : string
+            The name of the file to write to. 
+        fields : list of strings, optional
+            The fields to write to the file. If not specified
+            all of the fields in the buffer will be written.
+        clobber : boolean, optional
+            Whether or not to overwrite a previously existing file.
+            Default: False
+        All other keyword arguments are passed to the `writeto`
+        method of `astropy.io.fits.HDUList`.
+        """
+        if fields is None:
+            hdus = self.hdulist
+        else:
+            hdus = pyfits.HDUList()
+            for field in fields:
+                hdus.append(self.hdulist[field])
+        hdus.writeto(fileobj, clobber=clobber, **kwargs)
+
+    def info(self):
+        """
+        Display information about the underlying FITS file. 
+        """
+        self.hdulist.info()
 
     def to_glue(self, label="yt", data_collection=None):
         """
@@ -236,18 +274,18 @@
         `aplpy.FITSFigure` constructor.
         """
         import aplpy
-        return aplpy.FITSFigure(self, **kwargs)
-
-    def get_data(self, field):
-        return YTArray(self[field].data, self.field_units[field])
+        return aplpy.FITSFigure(self.hdulist, **kwargs)
 
     def set_unit(self, field, units):
         """
         Set the units of *field* to *units*.
         """
-        new_data = YTArray(self[field].data, self.field_units[field]).in_units(units)
-        self[field].data = new_data.v
-        self[field].header["bunit"] = units
+        if field not in self.keys():
+            raise KeyError("%s not an image!" % field)
+        new_data = self[field].in_units(units)
+        idx = self.fields.index(field)
+        self.hdulist[idx].data = new_data.v
+        self.hdulist[idx].header["bunit"] = units
         self.field_units[field] = units
 
 axis_wcs = [[1,2],[0,2],[0,1]]


https://bitbucket.org/yt_analysis/yt/commits/4b6df9381fc4/
Changeset:   4b6df9381fc4
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:19:00+00:00
Summary:     Specify a width for the entire FITS image instead of the pixel width, and figure out the latter that way.
Affected #:  1 file

diff -r f165aa37acd5f0b3e56f3b9aa2b9cfa6ce94d81b -r 4b6df9381fc45e4ba5fe63e1fe5e1d495c535b3d yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -50,10 +50,10 @@
             single array one field name must be specified.
         units : string
             The units of the WCS coordinates. Defaults to "cm".
-        pixel_scale : float
-            The scale of the pixel, in *units*. Either a single float or
-            iterable of floats. Only used if this information is not already
-            provided by *data*.
+        width : float or YTQuantity
+            The width of the image. Either a single value or iterable of values.
+            If a float, assumed to be in *units*. Only used if this information 
+            is not already provided by *data*.
         wcs : `astropy.wcs.WCS` instance, optional
             Supply an AstroPy WCS instance. Will override automatic WCS
             creation from FixedResolutionBuffers and YTCoveringGrids.
@@ -148,11 +148,13 @@
                 center = 0.5*(img_data.left_edge+img_data.right_edge).in_units(units).v
             else:
                 # If img_data is just an array, we assume the center is the origin
-                # and use *pixel_scale* to determine the cell widths
-                if iterable(pixel_scale):
-                    cdelt = pixel_scale
+                # and use the image width to determine the cell widths
+                if not iterable(width):
+                    width = [width]*self.dimensionality
+                if isinstance(width[0], YTQuantity):
+                    cdelt = [wh.in_units(units).v/n for wh, n in zip(width, self.shape)]
                 else:
-                    cdelt = [pixel_scale]*self.dimensionality
+                    cdelt = [wh/n for wh, n in zip(width, self.shape)]
                 center = [0.0]*self.dimensionality
             w.wcs.crpix = 0.5*(np.array(self.shape)+1)
             w.wcs.crval = center


https://bitbucket.org/yt_analysis/yt/commits/916129ccf00b/
Changeset:   916129ccf00b
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:38:17+00:00
Summary:     FITSImageBuffer --> FITSImageData and cleaning up some other things
Affected #:  1 file

diff -r 4b6df9381fc45e4ba5fe63e1fe5e1d495c535b3d -r 916129ccf00bed605526e2a1595884ff2e12ba45 yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -21,23 +21,17 @@
 pyfits = _astropy.pyfits
 pywcs = _astropy.pywcs
 
-if isinstance(pyfits, NotAModule):
-    HDUList = object
-else:
-    HDUList = pyfits.HDUList
+class FITSImageData(object):
 
-class FITSImageBuffer(HDUList):
+    def __init__(self, data, fields=None, units=None, width=None, wcs=None):
+        r""" Initialize a FITSImageData object.
 
-    def __init__(self, data, fields=None, units=None, pixel_scale=None, wcs=None):
-        r""" Initialize a FITSImageBuffer object.
-
-        FITSImageBuffer contains a list of FITS ImageHDU instances, and
-        optionally includes WCS information. It inherits from HDUList, so
-        operations such as `writeto` are enabled. Images can be constructed
-        from ImageArrays, NumPy arrays, dicts of such arrays,
-        FixedResolutionBuffers, and YTCoveringGrids. The latter two are the
-        most powerful because WCS information can be constructed from their
-        coordinates.
+        FITSImageData contains a collection of FITS ImageHDU instances and
+        WCS information, along with units for each of the images. FITSImageData
+        instances can be constructed from ImageArrays, NumPy arrays, dicts 
+        of such arrays, FixedResolutionBuffers, and YTCoveringGrids. The latter 
+        two are the most powerful because WCS information can be constructed 
+        automatically from their coordinates.
 
         Parameters
         ----------
@@ -77,46 +71,47 @@
         >>> w.wcs.ctype = ["RA---TAN","DEC--TAN"]
         >>> scale = 1./3600. # One arcsec per pixel
         >>> w.wcs.cdelt = [-scale, scale]
-        >>> f_deg = FITSImageBuffer(frb, fields="kT", wcs=w)
+        >>> f_deg = FITSImageData(frb, fields="kT", wcs=w)
         >>> f_deg.writeto("temp.fits")
         """
 
-        if units is None: units = "cm"
-        if pixel_scale is None: pixel_scale = 1.0
+        if units is None: 
+            units = "cm"
+        if width is None: 
+            width = 1.0
 
-        super(FITSImageBuffer, self).__init__()
+        exclude_fields = ['x','y','z','px','py','pz',
+                          'pdx','pdy','pdz','weight_field']
 
-        if isinstance(fields, string_types):
+        self.hdulist = pyfits.HDUList()
+
+        if isinstance(fields, string_types): 
             fields = [fields]
 
-        exclude_fields = ['x', 'y', 'z', 'px', 'py', 'pz',
-                          'pdx', 'pdy', 'pdz', 'weight_field']
-
         if hasattr(data, 'keys'):
             img_data = data
-        else:
-            img_data = {}
             if fields is None:
-                mylog.error("Please specify a field name for this array.")
-                raise KeyError("Please specify a field name for this array.")
-            img_data[fields[0]] = data
+                fields = list(img_data.keys())
+        elif isinstance(data, np.ndarray):
+            if fields is None:
+                mylog.warning("No field name given for this array. Calling it 'image_data'.")
+                fn = 'image_data'
+                fields = [fn]
+            else:
+                fn = fields[0]
+            img_data = {fn: data}
 
-        if fields is None: fields = img_data.keys()
-        if len(fields) == 0:
-            mylog.error("Please specify one or more fields to write.")
-            raise KeyError("Please specify one or more fields to write.")
+        self.fields = fields
 
         first = True
-
         self.field_units = {}
-
         for key in fields:
             if key not in exclude_fields:
                 if hasattr(img_data[key], "units"):
                     self.field_units[key] = str(img_data[key].units)
                 else:
                     self.field_units[key] = "dimensionless"
-                mylog.info("Making a FITS image of field %s" % (key))
+                mylog.info("Making a FITS image of field %s" % key)
                 if first:
                     hdu = pyfits.PrimaryHDU(np.array(img_data[key]))
                     first = False


https://bitbucket.org/yt_analysis/yt/commits/f49b7db74d04/
Changeset:   f49b7db74d04
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:39:50+00:00
Summary:     Use one method to update headers, either just one or all of them at once
Affected #:  1 file

diff -r 916129ccf00bed605526e2a1595884ff2e12ba45 -r f49b7db74d04fc570b363d90b96d953d8389f45f yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -171,12 +171,20 @@
             for k, v in h.items():
                 img.header[k] = v
 
-    def update_all_headers(self, key, value):
+    def update_header(self, field, key, value):
         """
-        Update the FITS headers for all images with the
-        same *key*, *value* pair.
+        Update the FITS header for *field* with a
+        *key*, *value* pair. If *field* == "all", all 
+        headers will be updated.
         """
-        for img in self: img.header[key] = value
+        if field == "all":
+            for img in self.hdulist:
+                img.header[key] = value
+        else:
+            if field not in self.keys():
+                raise KeyError("%s not an image!" % field)
+            idx = self.fields.index(field)
+            self.hdulist[idx].header[key] = value
 
     def keys(self):
         return self.fields


https://bitbucket.org/yt_analysis/yt/commits/bfd2f0e2f7e9/
Changeset:   bfd2f0e2f7e9
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:41:16+00:00
Summary:     Pop a FITS image from a FITSImageData instance and create a new instance from it
Affected #:  1 file

diff -r f49b7db74d04fc570b363d90b96d953d8389f45f -r bfd2f0e2f7e9718961948bf5313cde707b81dc34 yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -293,7 +293,20 @@
         self.hdulist[idx].header["bunit"] = units
         self.field_units[field] = units
 
-axis_wcs = [[1,2],[0,2],[0,1]]
+    def pop(self, key):
+        """
+        Remove a field with name *key*
+        and return it as a new FITSImageData 
+        instance.
+        """
+        if key not in self.keys():
+            raise KeyError("%s not an image!" % key)
+        data = self[key]
+        idx = self.fields.index(key)
+        self.hdulist.pop(idx)
+        self.field_units.pop(key)
+        self.fields.remove(key)
+        return FITSImageData(data, fields=key, wcs=self.wcs)
 
 def create_sky_wcs(old_wcs, sky_center, sky_scale,
                    ctype=["RA---TAN","DEC--TAN"], crota=None):


https://bitbucket.org/yt_analysis/yt/commits/059a6449789d/
Changeset:   059a6449789d
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:43:49+00:00
Summary:     Add classmethods to create new FITSImageData from files or from lists of FITSImageData. create_sky_wcs should be a method of FITSImageData.
Affected #:  1 file

diff -r bfd2f0e2f7e9718961948bf5313cde707b81dc34 -r 059a6449789dbf18dbdc534f148e3e6fc5e04e54 yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -308,51 +308,103 @@
         self.fields.remove(key)
         return FITSImageData(data, fields=key, wcs=self.wcs)
 
-def create_sky_wcs(old_wcs, sky_center, sky_scale,
-                   ctype=["RA---TAN","DEC--TAN"], crota=None):
-    """
-    Takes an astropy.wcs.WCS instance created in yt from a
-    simulation that has a Cartesian coordinate system and
-    converts it to one in a celestial coordinate system.
+    @classmethod
+    def from_file(cls, filename):
+        """
+        Generate a FITSImageData instance from one previously written to 
+        disk.
 
-    Parameters
-    ----------
-    old_wcs : astropy.wcs.WCS
-        The original WCS to be converted.
-    sky_center : tuple
-        Reference coordinates of the WCS in degrees.
-    sky_scale : tuple
-        Conversion between an angle unit and a length unit,
-        e.g. (3.0, "arcsec/kpc")
-    ctype : list of strings, optional
-        The type of the coordinate system to create.
-    crota : list of floats, optional
-        Rotation angles between cartesian coordinates and
-        the celestial coordinates.
-    """
-    naxis = old_wcs.naxis
-    crval = [sky_center[0], sky_center[1]]
-    scaleq = YTQuantity(sky_scale[0],sky_scale[1])
-    deltas = old_wcs.wcs.cdelt
-    units = [str(unit) for unit in old_wcs.wcs.cunit]
-    new_dx = (YTQuantity(-deltas[0], units[0])*scaleq).in_units("deg")
-    new_dy = (YTQuantity(deltas[1], units[1])*scaleq).in_units("deg")
-    new_wcs = pywcs.WCS(naxis=naxis)
-    cdelt = [new_dx.v, new_dy.v]
-    cunit = ["deg"]*2
-    if naxis == 3:
-        crval.append(old_wcs.wcs.crval[2])
-        cdelt.append(old_wcs.wcs.cdelt[2])
-        ctype.append(old_wcs.wcs.ctype[2])
-        cunit.append(old_wcs.wcs.cunit[2])
-    new_wcs.wcs.crpix = old_wcs.wcs.crpix
-    new_wcs.wcs.cdelt = cdelt
-    new_wcs.wcs.crval = crval
-    new_wcs.wcs.cunit = cunit
-    new_wcs.wcs.ctype = ctype
-    if crota is not None:
-        new_wcs.wcs.crota = crota
-    return new_wcs
+        Parameters
+        ----------
+        filename : string
+            The name of the file to open.
+        """
+        f = pyfits.open(filename)
+        data = {}
+        for hdu in f:
+            data[hdu.header["btype"]] = YTArray(hdu.data, hdu.header["bunit"])
+        f.close()
+        return cls(data, wcs=pywcs.WCS(header=hdu.header))
+
+    @classmethod
+    def from_images(cls, image_list):
+        """
+        Generate a new FITSImageData instance from a list of FITSImageData 
+        instances.
+
+        Parameters
+        ----------
+        image_list : list of FITSImageData instances
+            The images to be combined.
+        """
+        w = image_list[0].wcs
+        img_shape = image_list[0].shape
+        data = {}
+        for image in image_list:
+            assert_same_wcs(w, image.wcs)
+            if img_shape != image.shape:
+                raise RuntimeError("Images do not have the same shape!")
+            for k,v in image.items():
+                data[k] = v
+        return cls(data, wcs=w)
+
+    def create_sky_wcs(self, sky_center, sky_scale,
+                       ctype=["RA---TAN","DEC--TAN"], 
+                       crota=None, cd=None, pc=None):
+        """
+        Takes a Cartesian WCS and converts it to one in a 
+        celestial coordinate system.
+
+        Parameters
+        ----------
+        sky_center : iterable of floats
+            Reference coordinates of the WCS in degrees.
+        sky_scale : tuple or YTQuantity
+            Conversion between an angle unit and a length unit,
+            e.g. (3.0, "arcsec/kpc")
+        ctype : list of strings, optional
+            The type of the coordinate system to create.
+        crota : 2-element ndarray, optional
+            Rotation angles between cartesian coordinates and
+            the celestial coordinates.
+        cd : 2x2-element ndarray, optional
+            Dimensioned coordinate transformation matrix.
+        pc : 2x2-element ndarray, optional
+            Coordinate transformation matrix.
+        """
+        old_wcs = self.wcs
+        naxis = old_wcs.naxis
+        crval = [sky_center[0], sky_center[1]]
+        if isinstance(sky_scale, YTQuantity):
+            scaleq = sky_scale
+        else:
+            scaleq = YTQuantity(sky_scale[0],sky_scale[1])
+        if scaleq.units.dimensions != dimensions.angle/dimensions.length:
+            raise RuntimeError("sky_scale %s not in correct dimensions of angle/length!" % sky_scale)
+        deltas = old_wcs.wcs.cdelt
+        units = [str(unit) for unit in old_wcs.wcs.cunit]
+        new_dx = (YTQuantity(-deltas[0], units[0])*scaleq).in_units("deg")
+        new_dy = (YTQuantity(deltas[1], units[1])*scaleq).in_units("deg")
+        new_wcs = pywcs.WCS(naxis=naxis)
+        cdelt = [new_dx.v, new_dy.v]
+        cunit = ["deg"]*2
+        if naxis == 3:
+            crval.append(old_wcs.wcs.crval[2])
+            cdelt.append(old_wcs.wcs.cdelt[2])
+            ctype.append(old_wcs.wcs.ctype[2])
+            cunit.append(old_wcs.wcs.cunit[2])
+        new_wcs.wcs.crpix = old_wcs.wcs.crpix
+        new_wcs.wcs.cdelt = cdelt
+        new_wcs.wcs.crval = crval
+        new_wcs.wcs.cunit = cunit
+        new_wcs.wcs.ctype = ctype
+        if crota is not None:
+            new_wcs.wcs.crota = crota
+        if cd is not None:
+            new_wcs.wcs.cd = cd
+        if pc is not None:
+            new_wcs.wcs.cd = pc
+        self.set_wcs(new_wcs)
 
 def sanitize_fits_unit(unit):
     if unit == "Mpc":


https://bitbucket.org/yt_analysis/yt/commits/dd335f94afe6/
Changeset:   dd335f94afe6
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:44:49+00:00
Summary:     Adding FITSOffAxisSlice and FITSOffAxisProjection classes. Making some other necessary changes.
Affected #:  1 file

diff -r 059a6449789dbf18dbdc534f148e3e6fc5e04e54 -r dd335f94afe6d2b0bfed215629983aa9867dc0a2 yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -16,6 +16,10 @@
 from yt.data_objects.construction_data_containers import YTCoveringGridBase
 from yt.utilities.on_demand_imports import _astropy, NotAModule
 from yt.units.yt_array import YTQuantity, YTArray
+from yt.units import dimensions
+from yt.utilities.parallel_tools.parallel_analysis_interface import \
+    parallel_root_only
+from yt.visualization.volume_rendering.camera import off_axis_projection
 import re
 
 pyfits = _astropy.pyfits
@@ -414,11 +418,9 @@
         unit = "AU"
     return unit
 
-def construct_image(data_source, center=None, width=None, image_res=None):
-    ds = data_source.ds
-    axis = data_source.axis
-    if center is None or width is None:
-        center = ds.domain_center[axis_wcs[axis]]
+axis_wcs = [[1,2],[0,2],[0,1]]
+
+def construct_image(ds, axis, data_source, center, width=None, image_res=None):
     if width is None:
         width = ds.domain_width[axis_wcs[axis]]
         unit = ds.get_smallest_appropriate_unit(width[0])
@@ -428,28 +430,28 @@
         width = ds.coordinates.sanitize_width(axis, width, None)
         unit = str(width[0].units)
     if image_res is None:
-        dd = ds.all_data()
-        dx, dy = [dd.quantities.extrema("d%s" % "xyz"[idx])[0]
-                  for idx in axis_wcs[axis]]
-        nx = int((width[0]/dx).in_units("dimensionless"))
-        ny = int((width[1]/dy).in_units("dimensionless"))
+        ddims = ds.domain_dimensions*2**ds.index.max_level
+        if iterable(axis):
+            nx = ddims.max()
+            ny = ddims.max()
+        else:
+            nx, ny = [ddims[idx] for idx in axis_wcs[axis]]
     else:
         if iterable(image_res):
             nx, ny = image_res
         else:
             nx, ny = image_res, image_res
-        dx, dy = width[0]/nx, width[1]/ny
+    dx, dy = width[0]/nx, width[1]/ny
     crpix = [0.5*(nx+1), 0.5*(ny+1)]
-    if hasattr(ds, "wcs"):
+    if hasattr(ds, "wcs") and not iterable(axis):
         # This is a FITS dataset, so we use it to construct the WCS
         cunit = [str(ds.wcs.wcs.cunit[idx]) for idx in axis_wcs[axis]]
         ctype = [ds.wcs.wcs.ctype[idx] for idx in axis_wcs[axis]]
         cdelt = [ds.wcs.wcs.cdelt[idx] for idx in axis_wcs[axis]]
         ctr_pix = center.in_units("code_length")[:ds.dimensionality].v
-        crval = ds.wcs.wcs_pix2world(ctr_pix.reshape(1,ds.dimensionality))[0]
+        crval = ds.wcs.wcs_pix2world(ctr_pix.reshape(1, ds.dimensionality))[0]
         crval = [crval[idx] for idx in axis_wcs[axis]]
     else:
-        # This is some other kind of dataset                                                                      
         if unit == "unitary":
             unit = ds.get_smallest_appropriate_unit(ds.domain_width.max())
         elif unit == "code_length":
@@ -458,8 +460,17 @@
         cunit = [unit]*2
         ctype = ["LINEAR"]*2
         cdelt = [dx.in_units(unit)]*2
-        crval = [center[idx].in_units(unit) for idx in axis_wcs[axis]]
-    frb = data_source.to_frb(width[0], (nx,ny), center=center, height=width[1])
+        if iterable(axis):
+            crval = center.in_units(unit)
+        else:
+            crval = [center[idx].in_units(unit) for idx in axis_wcs[axis]]
+    if hasattr(data_source, 'to_frb'):
+        if iterable(axis):
+            frb = data_source.to_frb(width[0], (nx, ny), height=width[1])
+        else:
+            frb = data_source.to_frb(width[0], (nx, ny), center=center, height=width[1])
+    else:
+        frb = None
     w = pywcs.WCS(naxis=2)
     w.wcs.crpix = crpix
     w.wcs.cdelt = cdelt
@@ -468,7 +479,35 @@
     w.wcs.ctype = ctype
     return w, frb
 
-class FITSSlice(FITSImageBuffer):
+def assert_same_wcs(wcs1, wcs2):
+    from numpy.testing import assert_allclose
+    assert wcs1.naxis == wcs2.naxis
+    for i in range(wcs1.naxis):
+        assert wcs1.wcs.cunit[i] == wcs2.wcs.cunit[i]
+        assert wcs1.wcs.ctype[i] == wcs2.wcs.ctype[i]
+    assert_allclose(wcs1.wcs.crpix, wcs2.wcs.crpix)
+    assert_allclose(wcs1.wcs.cdelt, wcs2.wcs.cdelt)
+    assert_allclose(wcs1.wcs.crval, wcs2.wcs.crval)
+    crota1 = getattr(wcs1.wcs, "crota", None)
+    crota2 = getattr(wcs2.wcs, "crota", None)
+    if crota1 is None or crota2 is None:
+        assert crota1 == crota2
+    else:
+        assert_allclose(wcs1.wcs.crota, wcs2.wcs.crota)
+    cd1 = getattr(wcs1.wcs, "cd", None)
+    cd2 = getattr(wcs2.wcs, "cd", None)
+    if cd1 is None or cd2 is None:
+        assert cd1 == cd2
+    else:
+        assert_allclose(wcs1.wcs.cd, wcs2.wcs.cd)
+    pc1 = getattr(wcs1.wcs, "pc", None)
+    pc2 = getattr(wcs2.wcs, "pc", None)
+    if pc1 is None or pc2 is None:
+        assert pc1 == pc2
+    else:
+        assert_allclose(wcs1.wcs.pc, wcs2.wcs.pc)
+
+class FITSSlice(FITSImageData):
     r"""
     Generate a FITSImageData of an on-axis slice.
 
@@ -519,20 +558,18 @@
         axis = fix_axis(axis, ds)
         center, dcenter = ds.coordinates.sanitize_center(center, axis)
         slc = ds.slice(axis, center[axis], **kwargs)
-        w, frb = construct_image(slc, center=dcenter, width=width,
-                                 image_res=image_res)
+        w, frb = construct_image(ds, axis, slc, dcenter, width=width, image_res=image_res)
         super(FITSSlice, self).__init__(frb, fields=fields, wcs=w)
-        for i, field in enumerate(fields):
-            self[i].header["bunit"] = str(frb[field].units)
 
-class FITSProjection(FITSImageBuffer):
+
+class FITSProjection(FITSImageData):
     r"""
-    Generate a FITSImageBuffer of an on-axis projection.
+    Generate a FITSImageData of an on-axis projection.
 
     Parameters
     ----------
-    ds : FITSDataset
-        The FITS dataset object.
+    ds : :class:`yt.data_objects.api.Dataset`
+        The dataset object.
     axis : character or integer
         The axis along which to project. One of "x","y","z", or 0,1,2.
     fields : string or list of strings
@@ -579,8 +616,155 @@
         axis = fix_axis(axis, ds)
         center, dcenter = ds.coordinates.sanitize_center(center, axis)
         prj = ds.proj(fields[0], axis, weight_field=weight_field, **kwargs)
-        w, frb = construct_image(prj, center=dcenter, width=width,
-                                 image_res=image_res)
+        w, frb = construct_image(ds, axis, prj, dcenter, width=width, image_res=image_res)
         super(FITSProjection, self).__init__(frb, fields=fields, wcs=w)
-        for i, field in enumerate(fields):
-            self[i].header["bunit"] = str(frb[field].units)
+
+class FITSOffAxisSlice(FITSImageData):
+    r"""
+    Generate a FITSImageData of an off-axis slice.
+
+    Parameters
+    ----------
+    ds : :class:`yt.data_objects.api.Dataset`
+        The dataset object.
+    normal : a sequence of floats
+        The vector normal to the projection plane.
+    fields : string or list of strings
+        The fields to slice
+    center : A sequence of floats, a string, or a tuple.
+        The coordinate of the center of the image. If set to 'c', 'center' or
+        left blank, the plot is centered on the middle of the domain. If set to
+        'max' or 'm', the center will be located at the maximum of the
+        ('gas', 'density') field. Centering on the max or min of a specific
+        field is supported by providing a tuple such as ("min","temperature") or
+        ("max","dark_matter_density"). Units can be specified by passing in *center*
+        as a tuple containing a coordinate and string unit name or by passing
+        in a YTArray. If a list or unitless array is supplied, code units are
+        assumed.
+    width : tuple or a float.
+        Width can have four different formats to support windows with variable
+        x and y widths.  They are:
+
+        ==================================     =======================
+        format                                 example
+        ==================================     =======================
+        (float, string)                        (10,'kpc')
+        ((float, string), (float, string))     ((10,'kpc'),(15,'kpc'))
+        float                                  0.2
+        (float, float)                         (0.2, 0.3)
+        ==================================     =======================
+
+        For example, (10, 'kpc') requests a plot window that is 10 kiloparsecs
+        wide in the x and y directions, ((10,'kpc'),(15,'kpc')) requests a
+        window that is 10 kiloparsecs wide along the x axis and 15
+        kiloparsecs wide along the y axis.  In the other two examples, code
+        units are assumed, for example (0.2, 0.3) requests a plot that has an
+        x width of 0.2 and a y width of 0.3 in code units.  If units are
+        provided the resulting plot axis labels will use the supplied units.
+    image_res : an int or 2-tuple of ints
+        Specify the resolution of the resulting image.
+    north_vector : a sequence of floats
+        A vector defining the 'up' direction in the plot.  This
+        option sets the orientation of the slicing plane.  If not
+        set, an arbitrary grid-aligned north-vector is chosen.
+    """
+    def __init__(self, ds, normal, fields, center='c', width=None, image_res=512, 
+                 north_vector=None):
+        fields = ensure_list(fields)
+        center, dcenter = ds.coordinates.sanitize_center(center, 4)
+        cut = ds.cutting(normal, center, north_vector=north_vector)
+        center = ds.arr([0.0] * 2, 'code_length')
+        w, frb = construct_image(ds, normal, cut, center, width=width, image_res=image_res)
+        super(FITSOffAxisSlice, self).__init__(frb, fields=fields, wcs=w)
+
+
+class FITSOffAxisProjection(FITSImageData):
+    r"""
+    Generate a FITSImageData of an off-axis projection.
+
+    Parameters
+    ----------
+    ds : :class:`yt.data_objects.api.Dataset`
+        This is the dataset object corresponding to the
+        simulation output to be plotted.
+    normal : a sequence of floats
+        The vector normal to the projection plane.
+    fields : string, list of strings
+        The name of the field(s) to be plotted.
+    center : A sequence of floats, a string, or a tuple.
+         The coordinate of the center of the image. If set to 'c', 'center' or
+         left blank, the plot is centered on the middle of the domain. If set to
+         'max' or 'm', the center will be located at the maximum of the
+         ('gas', 'density') field. Centering on the max or min of a specific
+         field is supported by providing a tuple such as ("min","temperature") or
+         ("max","dark_matter_density"). Units can be specified by passing in *center*
+         as a tuple containing a coordinate and string unit name or by passing
+         in a YTArray. If a list or unitless array is supplied, code units are
+         assumed.
+    width : tuple or a float.
+         Width can have four different formats to support windows with variable
+         x and y widths.  They are:
+
+         ==================================     =======================
+         format                                 example
+         ==================================     =======================
+         (float, string)                        (10,'kpc')
+         ((float, string), (float, string))     ((10,'kpc'),(15,'kpc'))
+         float                                  0.2
+         (float, float)                         (0.2, 0.3)
+         ==================================     =======================
+
+         For example, (10, 'kpc') requests a plot window that is 10 kiloparsecs
+         wide in the x and y directions, ((10,'kpc'),(15,'kpc')) requests a
+         window that is 10 kiloparsecs wide along the x axis and 15
+         kiloparsecs wide along the y axis.  In the other two examples, code
+         units are assumed, for example (0.2, 0.3) requests a plot that has an
+         x width of 0.2 and a y width of 0.3 in code units.  If units are
+         provided the resulting plot axis labels will use the supplied units.
+    depth : A tuple or a float
+         A tuple containing the depth to project through and the string
+         key of the unit: (width, 'unit').  If set to a float, code units
+         are assumed
+    weight_field : string
+         The name of the weighting field.  Set to None for no weight.
+    image_res : an int or 2-tuple of ints
+        Specify the resolution of the resulting image. 
+    depth_res : an int 
+        Specify the resolution of the depth of the projection.
+    north_vector : a sequence of floats
+         A vector defining the 'up' direction in the plot.  This
+         option sets the orientation of the slicing plane.  If not
+         set, an arbitrary grid-aligned north-vector is chosen.
+    method : string
+         The method of projection.  Valid methods are:
+
+         "integrate" with no weight_field specified : integrate the requested
+         field along the line of sight.
+
+         "integrate" with a weight_field specified : weight the requested
+         field by the weighting field and integrate along the line of sight.
+
+         "sum" : This method is the same as integrate, except that it does not
+         multiply by a path length when performing the integration, and is
+         just a straight summation of the field along the given axis. WARNING:
+         This should only be used for uniform resolution grid datasets, as other
+         datasets may result in unphysical images.
+    """
+    def __init__(self, ds, normal, fields, center='c', width=(1.0, 'unitary'), 
+                 weight_field=None, image_res=512, depth_res=256, 
+                 north_vector=None, depth=(1.0,"unitary"), no_ghost=False, method='integrate'):
+        fields = ensure_list(fields)
+        center, dcenter = ds.coordinates.sanitize_center(center, 4)
+        buf = {}
+        width = ds.coordinates.sanitize_width(normal, width, depth)
+        wd = tuple(el.in_units('code_length').v for el in width)
+        if not iterable(image_res):
+            image_res = (image_res, image_res)
+        res = (image_res[0], image_res[1], depth_res)
+        for field in fields:
+            buf[field] = off_axis_projection(ds, center, normal, wd, res, field, 
+                                             no_ghost=no_ghost, north_vector=north_vector, 
+                                             method=method, weight=weight_field).swapaxes(0, 1)
+        center = ds.arr([0.0] * 2, 'code_length')
+        w, not_an_frb = construct_image(ds, normal, buf, center, width=width, image_res=image_res)
+        super(FITSOffAxisProjection, self).__init__(buf, fields=fields, wcs=w)


https://bitbucket.org/yt_analysis/yt/commits/a213dfc2cff8/
Changeset:   a213dfc2cff8
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:45:31+00:00
Summary:     Catch sunyaev_zeldovich up with the new FITSImageData changes.
Affected #:  1 file

diff -r dd335f94afe6d2b0bfed215629983aa9867dc0a2 -r a213dfc2cff8d3dced45dba2b2bc31073fb052b8 yt/analysis_modules/sunyaev_zeldovich/projection.py
--- a/yt/analysis_modules/sunyaev_zeldovich/projection.py
+++ b/yt/analysis_modules/sunyaev_zeldovich/projection.py
@@ -316,7 +316,7 @@
         >>> sky_center = (30., 45., "deg")
         >>> szprj.write_fits("SZbullet.fits", sky_center=sky_center, sky_scale=sky_scale)
         """
-        from yt.utilities.fits_image import FITSImageBuffer, create_sky_wcs
+        from yt.utilities.fits_image import FITSImageData
 
         dx = self.dx.in_units("kpc")
         dy = dx
@@ -328,10 +328,9 @@
         w.wcs.cunit = ["kpc"]*2
         w.wcs.ctype = ["LINEAR"]*2
 
+        fib = FITSImageData(self.data, fields=self.data.keys(), wcs=w)
         if sky_scale is not None and sky_center is not None:
-            w = create_sky_wcs(w, sky_center, sky_scale)
-
-        fib = FITSImageBuffer(self.data, fields=self.data.keys(), wcs=w)
+            fib.create_sky_wcs(sky_center, sky_scale)
         fib.writeto(filename, clobber=clobber)
         
     @parallel_root_only


https://bitbucket.org/yt_analysis/yt/commits/47efdc422932/
Changeset:   47efdc422932
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:46:01+00:00
Summary:     Implement the new FITSImageData changes in ppv_cube, and some small cosmetic changes to the module
Affected #:  1 file

diff -r a213dfc2cff8d3dced45dba2b2bc31073fb052b8 -r 47efdc422932ca439f58244bcef87ceebadbffb2 yt/analysis_modules/ppv_cube/ppv_cube.py
--- a/yt/analysis_modules/ppv_cube/ppv_cube.py
+++ b/yt/analysis_modules/ppv_cube/ppv_cube.py
@@ -89,6 +89,8 @@
         dims : integer, optional
             The spatial resolution of the cube. Implies nx = ny, e.g. the 
             aspect ratio of the PPVCube's spatial dimensions is 1.
+        thermal_broad : boolean, optional
+            Whether or not to broaden the line using the gas temperature. Default: False.
         atomic_weight : float, optional
             Set this value to the atomic weight of the particle that is emitting the line
             if *thermal_broad* is True. Defaults to 56 (Fe).
@@ -152,9 +154,7 @@
                                "methods are supported in PPVCube.")
 
         dd = ds.all_data()
-
         fd = dd._determine_fields(field)[0]
-
         self.field_units = ds._get_field_info(fd).units
 
         self.vbins = ds.arr(np.linspace(velocity_bounds[0],
@@ -214,16 +214,6 @@
         self.ds.field_info.pop(("gas","intensity"))
         self.ds.field_info.pop(("gas","v_los"))
 
-    def create_intensity(self):
-        def _intensity(field, data):
-            v = self.current_v-data["v_los"].v
-            T = data["temperature"].v
-            w = ppv_utils.compute_weight(self.thermal_broad, self.dv_cgs,
-                                         self.particle_mass, v.flatten(), T.flatten())
-            w[np.isnan(w)] = 0.0
-            return data[self.field]*w.reshape(v.shape)
-        return _intensity
-
     def transform_spectral_axis(self, rest_value, units):
         """
         Change the units of the spectral axis to some equivalent unit, such
@@ -259,17 +249,18 @@
         self.dv = self.vbins[1]-self.vbins[0]
 
     @parallel_root_only
-    def write_fits(self, filename, clobber=True, length_unit=None,
+    def write_fits(self, filename, clobber=False, length_unit=None,
                    sky_scale=None, sky_center=None):
         r""" Write the PPVCube to a FITS file.
 
         Parameters
         ----------
         filename : string
-            The name of the file to write.
-        clobber : boolean
-            Whether or not to clobber an existing file with the same name.
-        length_unit : string
+            The name of the file to write to. 
+        clobber : boolean, optional
+            Whether to overwrite a file with the same name that already 
+            exists. Default False.
+        length_unit : string, optional
             The units to convert the coordinates to in the file.
         sky_scale : tuple, optional
             Conversion between an angle unit and a length unit, if sky
@@ -280,7 +271,8 @@
 
         Examples
         --------
-        >>> cube.write_fits("my_cube.fits", clobber=False, sky_scale=(1.0,"arcsec/kpc"))
+        >>> cube.write_fits("my_cube.fits", clobber=False, 
+        ...                 sky_scale=(1.0,"arcsec/kpc"), sky_center=(30.,45.))
         """
         vunit = fits_info[self.axis_type][0]
         vtype = fits_info[self.axis_type][1]
@@ -303,13 +295,11 @@
         w.wcs.cunit = [units,units,vunit]
         w.wcs.ctype = ["LINEAR","LINEAR",vtype]
 
+        fib = FITSImageData(self.data.transpose(), fields=self.field, wcs=w)
+        fib.update_all_headers("bunit", re.sub('()', '', str(self.proj_units)))
+        fib.update_all_headers("btype", self.field)
         if sky_scale is not None and sky_center is not None:
-            w = create_sky_wcs(w, sky_center, sky_scale)
-
-        fib = FITSImageBuffer(self.data.transpose(), fields=self.field, wcs=w)
-        fib[0].header["bunit"] = re.sub('()', '', str(self.proj_units))
-        fib[0].header["btype"] = self.field
-
+            fib.create_sky_wcs(sky_center, sky_scale)
         fib.writeto(filename, clobber=clobber)
 
     def __repr__(self):
@@ -320,3 +310,13 @@
 
     def __getitem__(self, item):
         return self.data[item]
+
+    def _create_intensity(self):
+        def _intensity(field, data):
+            v = self.current_v-data["v_los"].v
+            T = data["temperature"].v
+            w = ppv_utils.compute_weight(self.thermal_broad, self.dv_cgs,
+                                         self.particle_mass, v.flatten(), T.flatten())
+            w[np.isnan(w)] = 0.0
+            return data[self.field]*w.reshape(v.shape)
+        return _intensity


https://bitbucket.org/yt_analysis/yt/commits/082397fb64d1/
Changeset:   082397fb64d1
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:46:20+00:00
Summary:     Catching up fixed_resolution with the FITSImageData changes
Affected #:  1 file

diff -r 47efdc422932ca439f58244bcef87ceebadbffb2 -r 082397fb64d193f35f0bf485bed9bc46e15cc769 yt/visualization/fixed_resolution.py
--- a/yt/visualization/fixed_resolution.py
+++ b/yt/visualization/fixed_resolution.py
@@ -318,14 +318,14 @@
             requested.
         """
 
-        from yt.utilities.fits_image import FITSImageBuffer
+        from yt.utilities.fits_image import FITSImageData
 
         extra_fields = ['x','y','z','px','py','pz','pdx','pdy','pdz','weight_field']
         if fields is None: 
             fields = [field[-1] for field in self.data_source.field_data
                       if field not in extra_fields]
 
-        fib = FITSImageBuffer(self, fields=fields, units=units)
+        fib = FITSImageData(self, fields=fields, units=units)
         if other_keys is not None:
             for k,v in other_keys.items():
                 fib.update_all_headers(k,v)
@@ -410,7 +410,7 @@
 
     def __getitem__(self, item):
         if item in self.data: return self.data[item]
-        mylog.info("Making a fixed resolutuion buffer of (%s) %d by %d" % \
+        mylog.info("Making a fixed resolution buffer of (%s) %d by %d" % \
             (item, self.buff_size[0], self.buff_size[1]))
         dd = self.data_source
         width = self.ds.arr((self.bounds[1] - self.bounds[0],


https://bitbucket.org/yt_analysis/yt/commits/a57cf2c79d41/
Changeset:   a57cf2c79d41
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:46:37+00:00
Summary:     Catching up image_handling with the FITSImageData changes
Affected #:  1 file

diff -r 082397fb64d193f35f0bf485bed9bc46e15cc769 -r a57cf2c79d41f1385c17f5157e323de37824f7a9 yt/visualization/volume_rendering/image_handling.py
--- a/yt/visualization/volume_rendering/image_handling.py
+++ b/yt/visualization/volume_rendering/image_handling.py
@@ -33,14 +33,14 @@
         f.create_dataset("A", data=image[:,:,3])
         f.close()
     if fits:
-        from yt.utilities.fits_image import FITSImageBuffer
+        from yt.utilities.fits_image import FITSImageData
         data = {}
         data["r"] = image[:,:,0]
         data["g"] = image[:,:,1]
         data["b"] = image[:,:,2]
         data["a"] = image[:,:,3]
         nx, ny = data["r"].shape
-        fib = FITSImageBuffer(data)
+        fib = FITSImageData(data)
         fib.writeto('%s.fits'%fn,clobber=True)
 
 def import_rgba(name, h5=True):


https://bitbucket.org/yt_analysis/yt/commits/51fe799a7744/
Changeset:   51fe799a7744
Branch:      yt
User:        jzuhone
Date:        2015-05-15 14:46:52+00:00
Summary:     FITSImageData tests
Affected #:  1 file

diff -r a57cf2c79d41f1385c17f5157e323de37824f7a9 -r 51fe799a7744a407967da2f116635437203a4b80 yt/utilities/tests/test_fits_image.py
--- /dev/null
+++ b/yt/utilities/tests/test_fits_image.py
@@ -0,0 +1,128 @@
+"""
+Unit test FITS image creation in yt.
+
+
+
+"""
+
+#-----------------------------------------------------------------------------
+# Copyright (c) 2013, yt Development Team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file COPYING.txt, distributed with this software.
+#-----------------------------------------------------------------------------
+
+import tempfile
+import os
+import numpy as np
+import shutil
+from yt.testing import fake_random_ds
+from yt.convenience import load
+from numpy.testing import \
+    assert_equal
+from yt.utilities.fits_image import \
+    FITSImageData, FITSProjection, \
+    FITSSlice, FITSOffAxisSlice, \
+    FITSOffAxisProjection, \
+    assert_same_wcs
+from yt.visualization.volume_rendering.camera import \
+    off_axis_projection
+
+def test_fits_image():
+    tmpdir = tempfile.mkdtemp()
+    curdir = os.getcwd()
+    os.chdir(tmpdir)
+
+    fields = ("density", "temperature")
+    units = ('g/cm**3', 'K',)
+    ds = fake_random_ds(64, fields=fields, units=units, nprocs=16,
+                        length_unit=100.0)
+
+    prj = ds.proj("density", 2)
+    prj_frb = prj.to_frb((0.5, "unitary"), 128)
+
+    fid1 = FITSImageData(prj_frb, fields=["density","temperature"], units="cm")
+    fits_prj = FITSProjection(ds, "z", ["density","temperature"], image_res=128,
+                              width=(0.5,"unitary"))
+
+    yield assert_equal, fid1["density"], fits_prj["density"]
+    yield assert_equal, fid1["temperature"], fits_prj["temperature"]
+
+    fid1.writeto("fid1.fits", clobber=True)
+    new_fid1 = FITSImageData.from_file("fid1.fits")
+
+    yield assert_equal, fid1["density"], new_fid1["density"]
+    yield assert_equal, fid1["temperature"], new_fid1["temperature"]
+
+    ds2 = load("fid1.fits")
+    ds2.index
+
+    assert ("fits","density") in ds2.field_list
+    assert ("fits","temperature") in ds2.field_list
+
+    dw_cm = ds2.domain_width.in_units("cm")
+
+    assert dw_cm[0].v == 50.
+    assert dw_cm[1].v == 50.
+
+    slc = ds.slice(2, 0.5)
+    slc_frb = slc.to_frb((0.5, "unitary"), 128)
+
+    fid2 = FITSImageData(slc_frb, fields=["density","temperature"], units="cm")
+    fits_slc = FITSSlice(ds, "z", ["density","temperature"], image_res=128,
+                         width=(0.5,"unitary"))
+
+    yield assert_equal, fid2["density"], fits_slc["density"]
+    yield assert_equal, fid2["temperature"], fits_slc["temperature"]
+
+    dens_img = fid2.pop("density")
+    temp_img = fid2.pop("temperature")
+
+    # This already has some assertions in it, so we don't need to do anything
+    # with it other can just make one
+    fid_comb = FITSImageData.from_images([dens_img, temp_img])
+
+    cut = ds.cutting([0.1, 0.2, -0.9], [0.5, 0.42, 0.6])
+    cut_frb = cut.to_frb((0.5, "unitary"), 128)
+
+    fid3 = FITSImageData(cut_frb, fields=["density","temperature"], units="cm")
+    fits_cut = FITSOffAxisSlice(ds, [0.1, 0.2, -0.9], ["density","temperature"], 
+                                image_res=128, center=[0.5, 0.42, 0.6],
+                                width=(0.5,"unitary"))
+
+    yield assert_equal, fid3["density"], fits_cut["density"]
+    yield assert_equal, fid3["temperature"], fits_cut["temperature"]
+
+    fid3.create_sky_wcs([30.,45.], (1.0,"arcsec/kpc"))
+    fid3.writeto("fid3.fits", clobber=True)
+    new_fid3 = FITSImageData.from_file("fid3.fits")
+    assert_same_wcs(fid3.wcs, new_fid3.wcs)
+    assert new_fid3.wcs.wcs.cunit[0] == "deg"
+    assert new_fid3.wcs.wcs.cunit[1] == "deg"
+    assert new_fid3.wcs.wcs.ctype[0] == "RA---TAN"
+    assert new_fid3.wcs.wcs.ctype[1] == "DEC--TAN"
+
+    buf = off_axis_projection(ds, ds.domain_center, [0.1, 0.2, -0.9], 
+                              0.5, 128, "density").swapaxes(0, 1)
+    fid4 = FITSImageData(buf, fields="density", width=100.0)
+    fits_oap = FITSOffAxisProjection(ds, [0.1, 0.2, -0.9], "density", 
+                                     width=(0.5,"unitary"), image_res=128, 
+                                     depth_res=128, depth=(0.5,"unitary"))
+
+    yield assert_equal, fid4["density"], fits_oap["density"]
+
+    cvg = ds.covering_grid(ds.index.max_level, [0.25,0.25,0.25], 
+                           [32, 32, 32], fields=["density","temperature"])
+    fid5 = FITSImageData(cvg, fields=["density","temperature"])
+    assert fid5.dimensionality == 3
+
+    fid5.update_header("density", "time", 0.1)
+    fid5.update_header("all", "units", "cgs")
+    
+    assert fid5.get_header("density")["time"] == 0.1
+    assert fid5.get_header("temperature")["units"] == "cgs"
+    assert fid5.get_header("density")["units"] == "cgs"
+    
+    os.chdir(curdir)
+    shutil.rmtree(tmpdir)


https://bitbucket.org/yt_analysis/yt/commits/791fa17f0474/
Changeset:   791fa17f0474
Branch:      yt
User:        jzuhone
Date:        2015-05-29 02:30:05+00:00
Summary:     Updating docs for FITS images.
Affected #:  3 files

diff -r 51fe799a7744a407967da2f116635437203a4b80 -r 791fa17f047401a9c4db12bb60c61a7388de109f doc/source/visualizing/FITSImageBuffer.ipynb
--- a/doc/source/visualizing/FITSImageBuffer.ipynb
+++ /dev/null
@@ -1,205 +0,0 @@
-{
- "metadata": {
-  "name": "",
-  "signature": "sha256:872f7525edd3c1ee09c67f6ecdd8552218df05ebe5ab73bcab55654edf0ac2bb"
- },
- "nbformat": 3,
- "nbformat_minor": 0,
- "worksheets": [
-  {
-   "cells": [
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "yt has capabilities for writing 2D and 3D uniformly gridded data generated from datasets to FITS files. This is via the `FITSImageBuffer` class, which has subclasses `FITSSlice` and `FITSProjection` to write slices and projections directly to FITS. We'll test this out on an Athena dataset."
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "%matplotlib inline\n",
-      "import yt\n",
-      "from yt.utilities.fits_image import FITSImageBuffer, FITSSlice, FITSProjection"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "ds = yt.load(\"MHDSloshing/virgo_low_res.0054.vtk\", parameters={\"length_unit\":(1.0,\"Mpc\"),\n",
-      "                                                               \"mass_unit\":(1.0e14,\"Msun\"),\n",
-      "                                                               \"time_unit\":(1.0,\"Myr\")})"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "To demonstrate a useful example of creating a FITS file, let's first make a `ProjectionPlot`:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj = yt.ProjectionPlot(ds, \"z\", [\"temperature\"], weight_field=\"density\", width=(500.,\"kpc\"))\n",
-      "prj.show()"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Suppose that we wanted to write this projection to a FITS file for analysis and visualization in other programs, such as ds9. We can do that using `FITSProjection`:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits = FITSProjection(ds, \"z\", [\"temperature\"], weight_field=\"density\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "which took the same parameters as `ProjectionPlot` except the width, because `FITSProjection` and `FITSSlice` always make slices and projections of the width of the domain size, at the finest resolution available in the simulation, in a unit determined to be appropriate for the physical size of the dataset. `prj_fits` is a full-fledged FITS file in memory, specifically an [AstroPy `HDUList`](http://astropy.readthedocs.org/en/latest/io/fits/api/hdulists.html) object. This means that we can use all of the methods inherited from `HDUList`:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits.info()"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "`info` shows us the contents of the virtual FITS file. We can also look at the header for the `\"temperature\"` image, like so:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits[\"temperature\"].header"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "where we can see that the temperature units are in Kelvin and the cell widths are in kiloparsecs. The projection can be written to disk using the `writeto` method:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits.writeto(\"sloshing.fits\", clobber=True)"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Since yt can read FITS image files, it can be loaded up just like any other dataset:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "ds2 = yt.load(\"sloshing.fits\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "and we can make a `SlicePlot` of the 2D image, which shows the same data as the previous image:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "slc2 = yt.SlicePlot(ds2, \"z\", [\"temperature\"], width=(500.,\"kpc\"))\n",
-      "slc2.set_log(\"temperature\", True)\n",
-      "slc2.show()"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "If you want more fine-grained control over what goes into the FITS file, you can call `FITSImageBuffer` directly, with various kinds of inputs. For example, you could use a `FixedResolutionBuffer`, and specify you want the units in parsecs instead:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "slc3 = ds.slice(0, 0.0)\n",
-      "frb = slc3.to_frb((500.,\"kpc\"), 800)\n",
-      "fib = FITSImageBuffer(frb, fields=[\"density\",\"temperature\"], units=\"pc\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Finally, a 3D FITS cube can be created from a covering grid:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "cvg = ds.covering_grid(ds.index.max_level, [-0.5,-0.5,-0.5], [64, 64, 64], fields=[\"density\",\"temperature\"])\n",
-      "fib = FITSImageBuffer(cvg, fields=[\"density\",\"temperature\"], units=\"Mpc\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    }
-   ],
-   "metadata": {}
-  }
- ]
-}
\ No newline at end of file

diff -r 51fe799a7744a407967da2f116635437203a4b80 -r 791fa17f047401a9c4db12bb60c61a7388de109f doc/source/visualizing/FITSImageData.ipynb
--- /dev/null
+++ b/doc/source/visualizing/FITSImageData.ipynb
@@ -0,0 +1,392 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:904e7ea07d0e4df6a73f57089fc9cd8347b056f0e763d6a8c4782182d1b6e2bb"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "yt has capabilities for writing 2D and 3D uniformly gridded data generated from datasets to FITS files. This is via the `FITSImageData` class. We'll test these capabilities out on an Athena dataset."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "import yt\n",
+      "from yt.utilities.fits_image import FITSImageData, FITSProjection"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "ds = yt.load(\"MHDSloshing/virgo_low_res.0054.vtk\", parameters={\"length_unit\":(1.0,\"Mpc\"),\n",
+      "                                                               \"mass_unit\":(1.0e14,\"Msun\"),\n",
+      "                                                               \"time_unit\":(1.0,\"Myr\")})"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Creating FITS images from Slices and Projections"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "There are several ways to make a `FITSImageData` instance. The most intuitive ways are to use the `FITSSlice`, `FITSProjection`, `FITSOffAxisSlice`, and `FITSOffAxisProjection` classes to write slices and projections directly to FITS. To demonstrate a useful example of creating a FITS file, let's first make a `ProjectionPlot`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj = yt.ProjectionPlot(ds, \"z\", [\"temperature\"], weight_field=\"density\", width=(500.,\"kpc\"))\n",
+      "prj.show()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Suppose that we wanted to write this projection to a FITS file for analysis and visualization in other programs, such as ds9. We can do that using `FITSProjection`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits = FITSProjection(ds, \"z\", [\"temperature\"], weight_field=\"density\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "which took the same parameters as `ProjectionPlot` except the width, because `FITSProjection` and `FITSSlice` always make slices and projections of the width of the domain size, at the finest resolution available in the simulation, in a unit determined to be appropriate for the physical size of the dataset."
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      " `prj_fits` implements some methods from the [AstroPy `HDUList`](http://astropy.readthedocs.org/en/latest/io/fits/api/hdulists.html) class. `info` shows us the contents of the virtual FITS file:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "We can also look at the header for a particular field, using `get_header`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.get_header(\"temperature\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "where we can see that the temperature units are in Kelvin and the cell widths are in kiloparsecs. We can use the `set_unit` method to change the units of a particular field:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.set_unit(\"temperature\",\"R\")\n",
+      "print prj_fits[\"temperature\"]"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "The image can be written to disk using the `writeto` method:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.writeto(\"sloshing.fits\", clobber=True)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Since yt can read FITS image files, it can be loaded up just like any other dataset:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "ds2 = yt.load(\"sloshing.fits\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "and we can make a `SlicePlot` of the 2D image, which shows the same data as the previous image:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "slc2 = yt.SlicePlot(ds2, \"z\", [\"temperature\"], width=(500.,\"kpc\"))\n",
+      "slc2.set_log(\"temperature\", True)\n",
+      "slc2.show()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Using `FITSImageData` directly"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "If you want more fine-grained control over what goes into the FITS file, you can call `FITSImageData` directly, with various kinds of inputs. For example, you could use a `FixedResolutionBuffer`, and specify you want the units in parsecs instead:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "slc3 = ds.slice(0, 0.0)\n",
+      "frb = slc3.to_frb((500.,\"kpc\"), 800)\n",
+      "fid_frb = FITSImageData(frb, fields=[\"density\",\"temperature\"], units=\"pc\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "A 3D FITS cube can also be created from a covering grid:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "cvg = ds.covering_grid(ds.index.max_level, [-0.5,-0.5,-0.5], [64, 64, 64], fields=[\"density\",\"temperature\"])\n",
+      "fid_cvg = FITSImageData(cvg, fields=[\"density\",\"temperature\"], units=\"Mpc\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Other `FITSImageData` Methods"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "A `FITSImageData` instance can be generated from one previously written to disk using the `from_file` classmethod:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "fid = FITSImageData.from_file(\"sloshing.fits\")\n",
+      "fid.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Multiple `FITSImageData` can be combined to create a new one, provided that the coordinate information is the same:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits2 = FITSProjection(ds, \"z\", [\"density\"])\n",
+      "prj_fits3 = FITSImageData.from_images([prj_fits, prj_fits2])\n",
+      "prj_fits3.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Alternatively, individual fields can be popped as well:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "dens_fits = prj_fits3.pop(\"density\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "dens_fits.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits3.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "So far, the FITS images we have shown have linear spatial coordinates. One may want to take a projection of an object and make a crude mock observation out of it, with celestial coordinates. For this, we can use the `create_sky_wcs` method. Specify a center (RA, Dec) coordinate in degrees, as well as a linear scale in terms of angle per distance:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "sky_center = [30.,45.] # in degrees\n",
+      "sky_scale = (2.5, \"arcsec/kpc\") # could also use a YTQuantity\n",
+      "prj_fits.create_sky_wcs(sky_center, sky_scale, ctype=[\"RA---TAN\",\"DEC--TAN\"])"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "By the default, a tangent RA/Dec projection is used, but one could also use another projection using the `ctype` keyword. We can now look at the header and see it has the appropriate WCS now:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.get_header(\"temperature\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Finally, we can add header keywords to a single field or for all fields in the FITS image using `update_header`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "fid_frb.update_header(\"all\", \"time\", 0.1) # Update all the fields\n",
+      "fid_frb.update_header(\"temperature\", \"scale\", \"Rankine\") # Update just one field"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "print fid_frb.get_header(\"density\")[\"time\"]\n",
+      "print fid_frb.get_header(\"temperature\")[\"scale\"]"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
\ No newline at end of file

diff -r 51fe799a7744a407967da2f116635437203a4b80 -r 791fa17f047401a9c4db12bb60c61a7388de109f doc/source/visualizing/writing_fits_images.rst
--- a/doc/source/visualizing/writing_fits_images.rst
+++ b/doc/source/visualizing/writing_fits_images.rst
@@ -3,4 +3,4 @@
 Writing FITS Images
 ==========================
 
-.. notebook:: FITSImageBuffer.ipynb
\ No newline at end of file
+.. notebook:: FITSImageData.ipynb
\ No newline at end of file


https://bitbucket.org/yt_analysis/yt/commits/0e1aba8962f2/
Changeset:   0e1aba8962f2
Branch:      yt
User:        jzuhone
Date:        2015-05-29 05:07:19+00:00
Summary:     Forgot this in here
Affected #:  1 file

diff -r 791fa17f047401a9c4db12bb60c61a7388de109f -r 0e1aba8962f244487268becafc6ee53691f70330 yt/analysis_modules/ppv_cube/ppv_cube.py
--- a/yt/analysis_modules/ppv_cube/ppv_cube.py
+++ b/yt/analysis_modules/ppv_cube/ppv_cube.py
@@ -13,8 +13,7 @@
 import numpy as np
 from yt.utilities.on_demand_imports import _astropy
 from yt.utilities.orientation import Orientation
-from yt.utilities.fits_image import FITSImageBuffer, sanitize_fits_unit, \
-    create_sky_wcs
+from yt.utilities.fits_image import FITSImageData, sanitize_fits_unit
 from yt.visualization.volume_rendering.camera import off_axis_projection
 from yt.funcs import get_pbar
 from yt.utilities.physical_constants import clight, mh


https://bitbucket.org/yt_analysis/yt/commits/19aefe028c92/
Changeset:   19aefe028c92
Branch:      yt
User:        jzuhone
Date:        2015-05-29 05:08:47+00:00
Summary:     Decided to revert back to some original behaviors. Inheriting directly from HDUList. No longer overloading __getitem__.
Affected #:  1 file

diff -r 0e1aba8962f244487268becafc6ee53691f70330 -r 19aefe028c92212445658c43adab9cec771a4001 yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -25,7 +25,12 @@
 pyfits = _astropy.pyfits
 pywcs = _astropy.pywcs
 
-class FITSImageData(object):
+if isinstance(pyfits, NotAModule):
+    HDUList = object
+else:
+    HDUList = pyfits.HDUList
+
+class FITSImageData(HDUList):
 
     def __init__(self, data, fields=None, units=None, width=None, wcs=None):
         r""" Initialize a FITSImageData object.
@@ -79,17 +84,17 @@
         >>> f_deg.writeto("temp.fits")
         """
 
-        if units is None: 
+        if units is None:
             units = "cm"
-        if width is None: 
+        if width is None:
             width = 1.0
 
         exclude_fields = ['x','y','z','px','py','pz',
                           'pdx','pdy','pdz','weight_field']
 
-        self.hdulist = pyfits.HDUList()
+        super(FITSImageData, self).__init__()
 
-        if isinstance(fields, string_types): 
+        if isinstance(fields, string_types):
             fields = [fields]
 
         if hasattr(data, 'keys'):
@@ -125,13 +130,13 @@
                 hdu.header["btype"] = key
                 if hasattr(img_data[key], "units"):
                     hdu.header["bunit"] = re.sub('()', '', str(img_data[key].units))
-                self.hdulist.append(hdu)
+                self.append(hdu)
 
-        self.shape = self.hdulist[0].shape
+        self.shape = self[0].shape
         self.dimensionality = len(self.shape)
 
         if wcs is None:
-            w = pywcs.WCS(header=self.hdulist[0].header, naxis=self.dimensionality)
+            w = pywcs.WCS(header=self[0].header, naxis=self.dimensionality)
             if isinstance(img_data, FixedResolutionBuffer):
                 # FRBs are a special case where we have coordinate
                 # information, so we take advantage of this and
@@ -171,7 +176,7 @@
         """
         self.wcs = wcs
         h = self.wcs.to_header()
-        for img in self.hdulist:
+        for img in self:
             for k, v in h.items():
                 img.header[k] = v
 
@@ -182,23 +187,22 @@
         headers will be updated.
         """
         if field == "all":
-            for img in self.hdulist:
+            for img in self:
                 img.header[key] = value
         else:
             if field not in self.keys():
                 raise KeyError("%s not an image!" % field)
             idx = self.fields.index(field)
-            self.hdulist[idx].header[key] = value
+            self[idx].header[key] = value
+
+    def update_all_headers(self, key, value):
+        mylog.warning("update_all_headers is deprecated. "+
+                      "Use update_header('all', key, value) instead.")
+        self.update_header("all", key, value)
 
     def keys(self):
         return self.fields
 
-    def __getitem__(self, field):
-        if field not in self.keys():
-            raise KeyError("%s not an image!" % field)
-        idx = self.fields.index(field)
-        return YTArray(self.hdulist[idx].data, self.field_units[field])
-
     def has_key(self, key):
         return key in self.fields
 
@@ -208,20 +212,6 @@
     def items(self):
         return [(k, self[k]) for k in self.fields]
 
-    def get_header(self, field):
-        """
-        Get the FITS header for a specific field.
-
-        Parameters
-        ----------
-        field : string
-            The field for which to get the corresponding header. 
-        """
-        if field not in self.keys():
-            raise KeyError("%s not an image!" % field)
-        idx = self.fields.index(field)
-        return self.hdulist[idx].header
-
     @parallel_root_only
     def writeto(self, fileobj, fields=None, clobber=False, **kwargs):
         r"""
@@ -241,19 +231,13 @@
         method of `astropy.io.fits.HDUList`.
         """
         if fields is None:
-            hdus = self.hdulist
+            hdus = pyfits.HDUList(self)
         else:
             hdus = pyfits.HDUList()
             for field in fields:
-                hdus.append(self.hdulist[field])
+                hdus.append(self[field])
         hdus.writeto(fileobj, clobber=clobber, **kwargs)
 
-    def info(self):
-        """
-        Display information about the underlying FITS file. 
-        """
-        self.hdulist.info()
-
     def to_glue(self, label="yt", data_collection=None):
         """
         Takes the data in the FITSImageData instance and exports it to
@@ -267,8 +251,8 @@
 
         image = Data(label=label)
         image.coords = coordinates_from_header(self.wcs.to_header())
-        for k,v in self.items():
-            image.add_component(v.v, k)
+        for k,f in self.items():
+            image.add_component(f.data, k)
         if data_collection is None:
             dc = DataCollection([image])
             app = GlueApplication(dc)
@@ -283,7 +267,14 @@
         `aplpy.FITSFigure` constructor.
         """
         import aplpy
-        return aplpy.FITSFigure(self.hdulist, **kwargs)
+        return aplpy.FITSFigure(self, **kwargs)
+
+    def get_data(self, field):
+        """
+        Return the data array of the image corresponding to *field*
+        with units attached.
+        """
+        return YTArray(self[field].data, self.field_units[field])
 
     def set_unit(self, field, units):
         """
@@ -291,10 +282,10 @@
         """
         if field not in self.keys():
             raise KeyError("%s not an image!" % field)
-        new_data = self[field].in_units(units)
         idx = self.fields.index(field)
-        self.hdulist[idx].data = new_data.v
-        self.hdulist[idx].header["bunit"] = units
+        new_data = YTArray(self[idx].data, self.field_units[field]).in_units(units)
+        self[idx].data = new_data.v
+        self[idx].header["bunit"] = units
         self.field_units[field] = units
 
     def pop(self, key):
@@ -305,9 +296,8 @@
         """
         if key not in self.keys():
             raise KeyError("%s not an image!" % key)
-        data = self[key]
         idx = self.fields.index(key)
-        self.hdulist.pop(idx)
+        data = YTArray(super(FITSImageData, self).pop(idx), self.field_units[key])
         self.field_units.pop(key)
         self.fields.remove(key)
         return FITSImageData(data, fields=key, wcs=self.wcs)
@@ -353,10 +343,10 @@
         return cls(data, wcs=w)
 
     def create_sky_wcs(self, sky_center, sky_scale,
-                       ctype=["RA---TAN","DEC--TAN"], 
+                       ctype=["RA---TAN","DEC--TAN"],
                        crota=None, cd=None, pc=None):
         """
-        Takes a Cartesian WCS and converts it to one in a 
+        Takes a Cartesian WCS and converts it to one in a
         celestial coordinate system.
 
         Parameters
@@ -410,6 +400,9 @@
             new_wcs.wcs.cd = pc
         self.set_wcs(new_wcs)
 
+class FITSImageBuffer(FITSImageData):
+    pass
+
 def sanitize_fits_unit(unit):
     if unit == "Mpc":
         mylog.info("Changing FITS file unit to kpc.")
@@ -610,7 +603,7 @@
         Specify the resolution of the resulting image. If not provided, it will be
         determined based on the minimum cell size of the dataset.
     """
-    def __init__(self, ds, axis, fields, center="c", width=None, 
+    def __init__(self, ds, axis, fields, center="c", width=None,
                  weight_field=None, image_res=None, **kwargs):
         fields = ensure_list(fields)
         axis = fix_axis(axis, ds)
@@ -668,7 +661,7 @@
         option sets the orientation of the slicing plane.  If not
         set, an arbitrary grid-aligned north-vector is chosen.
     """
-    def __init__(self, ds, normal, fields, center='c', width=None, image_res=512, 
+    def __init__(self, ds, normal, fields, center='c', width=None, image_res=512,
                  north_vector=None):
         fields = ensure_list(fields)
         center, dcenter = ds.coordinates.sanitize_center(center, 4)
@@ -750,8 +743,8 @@
          This should only be used for uniform resolution grid datasets, as other
          datasets may result in unphysical images.
     """
-    def __init__(self, ds, normal, fields, center='c', width=(1.0, 'unitary'), 
-                 weight_field=None, image_res=512, depth_res=256, 
+    def __init__(self, ds, normal, fields, center='c', width=(1.0, 'unitary'),
+                 weight_field=None, image_res=512, depth_res=256,
                  north_vector=None, depth=(1.0,"unitary"), no_ghost=False, method='integrate'):
         fields = ensure_list(fields)
         center, dcenter = ds.coordinates.sanitize_center(center, 4)
@@ -762,8 +755,8 @@
             image_res = (image_res, image_res)
         res = (image_res[0], image_res[1], depth_res)
         for field in fields:
-            buf[field] = off_axis_projection(ds, center, normal, wd, res, field, 
-                                             no_ghost=no_ghost, north_vector=north_vector, 
+            buf[field] = off_axis_projection(ds, center, normal, wd, res, field,
+                                             no_ghost=no_ghost, north_vector=north_vector,
                                              method=method, weight=weight_field).swapaxes(0, 1)
         center = ds.arr([0.0] * 2, 'code_length')
         w, not_an_frb = construct_image(ds, normal, buf, center, width=width, image_res=image_res)


https://bitbucket.org/yt_analysis/yt/commits/04b4e2efd6da/
Changeset:   04b4e2efd6da
Branch:      yt
User:        jzuhone
Date:        2015-05-29 05:26:53+00:00
Summary:     Fixed some bugs
Affected #:  1 file

diff -r 19aefe028c92212445658c43adab9cec771a4001 -r 04b4e2efd6da316bb24d2a46ade57e781822f55e yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -297,7 +297,8 @@
         if key not in self.keys():
             raise KeyError("%s not an image!" % key)
         idx = self.fields.index(key)
-        data = YTArray(super(FITSImageData, self).pop(idx), self.field_units[key])
+        im = super(FITSImageData, self).pop(idx)
+        data = YTArray(im.data, self.field_units[key])
         self.field_units.pop(key)
         self.fields.remove(key)
         return FITSImageData(data, fields=key, wcs=self.wcs)
@@ -338,8 +339,8 @@
             assert_same_wcs(w, image.wcs)
             if img_shape != image.shape:
                 raise RuntimeError("Images do not have the same shape!")
-            for k,v in image.items():
-                data[k] = v
+            for key in image.keys():
+                data[key] = image.get_data(key)
         return cls(data, wcs=w)
 
     def create_sky_wcs(self, sky_center, sky_scale,


https://bitbucket.org/yt_analysis/yt/commits/6f7e872d6305/
Changeset:   6f7e872d6305
Branch:      yt
User:        jzuhone
Date:        2015-05-29 05:31:39+00:00
Summary:     Fixing tests
Affected #:  1 file

diff -r 04b4e2efd6da316bb24d2a46ade57e781822f55e -r 6f7e872d6305861d67ea0d7032e98825dc5159a2 yt/utilities/tests/test_fits_image.py
--- a/yt/utilities/tests/test_fits_image.py
+++ b/yt/utilities/tests/test_fits_image.py
@@ -46,14 +46,14 @@
     fits_prj = FITSProjection(ds, "z", ["density","temperature"], image_res=128,
                               width=(0.5,"unitary"))
 
-    yield assert_equal, fid1["density"], fits_prj["density"]
-    yield assert_equal, fid1["temperature"], fits_prj["temperature"]
+    yield assert_equal, fid1.get_data("density"), fits_prj.get_data("density")
+    yield assert_equal, fid1.get_data("temperature"), fits_prj.get_data("temperature")
 
     fid1.writeto("fid1.fits", clobber=True)
     new_fid1 = FITSImageData.from_file("fid1.fits")
 
-    yield assert_equal, fid1["density"], new_fid1["density"]
-    yield assert_equal, fid1["temperature"], new_fid1["temperature"]
+    yield assert_equal, fid1.get_data("density"), new_fid1.get_data("density")
+    yield assert_equal, fid1.get_data("temperature"), new_fid1.get_data("temperature")
 
     ds2 = load("fid1.fits")
     ds2.index
@@ -73,8 +73,8 @@
     fits_slc = FITSSlice(ds, "z", ["density","temperature"], image_res=128,
                          width=(0.5,"unitary"))
 
-    yield assert_equal, fid2["density"], fits_slc["density"]
-    yield assert_equal, fid2["temperature"], fits_slc["temperature"]
+    yield assert_equal, fid2.get_data("density"), fits_slc.get_data("density")
+    yield assert_equal, fid2.get_data("temperature"), fits_slc.get_data("temperature")
 
     dens_img = fid2.pop("density")
     temp_img = fid2.pop("temperature")
@@ -91,8 +91,8 @@
                                 image_res=128, center=[0.5, 0.42, 0.6],
                                 width=(0.5,"unitary"))
 
-    yield assert_equal, fid3["density"], fits_cut["density"]
-    yield assert_equal, fid3["temperature"], fits_cut["temperature"]
+    yield assert_equal, fid3.get_data("density"), fits_cut.get_data("density")
+    yield assert_equal, fid3.get_data("temperature"), fits_cut.get_data("temperature")
 
     fid3.create_sky_wcs([30.,45.], (1.0,"arcsec/kpc"))
     fid3.writeto("fid3.fits", clobber=True)
@@ -110,7 +110,7 @@
                                      width=(0.5,"unitary"), image_res=128, 
                                      depth_res=128, depth=(0.5,"unitary"))
 
-    yield assert_equal, fid4["density"], fits_oap["density"]
+    yield assert_equal, fid4.get_data("density"), fits_oap.get_data("density")
 
     cvg = ds.covering_grid(ds.index.max_level, [0.25,0.25,0.25], 
                            [32, 32, 32], fields=["density","temperature"])
@@ -120,9 +120,9 @@
     fid5.update_header("density", "time", 0.1)
     fid5.update_header("all", "units", "cgs")
     
-    assert fid5.get_header("density")["time"] == 0.1
-    assert fid5.get_header("temperature")["units"] == "cgs"
-    assert fid5.get_header("density")["units"] == "cgs"
+    assert fid5["density"].header["time"] == 0.1
+    assert fid5["temperature"].header["units"] == "cgs"
+    assert fid5["density"].header["units"] == "cgs"
     
     os.chdir(curdir)
     shutil.rmtree(tmpdir)


https://bitbucket.org/yt_analysis/yt/commits/e05cffc36d98/
Changeset:   e05cffc36d98
Branch:      yt
User:        jzuhone
Date:        2015-05-29 05:34:19+00:00
Summary:     Updated docs
Affected #:  1 file

diff -r 6f7e872d6305861d67ea0d7032e98825dc5159a2 -r e05cffc36d9812ba53fbfbc3bb5445929f1a3587 doc/source/visualizing/FITSImageData.ipynb
--- a/doc/source/visualizing/FITSImageData.ipynb
+++ b/doc/source/visualizing/FITSImageData.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:904e7ea07d0e4df6a73f57089fc9cd8347b056f0e763d6a8c4782182d1b6e2bb"
+  "signature": "sha256:c7de5ef190feaa2289595aec7eaa05db02fd535e408e0d04aa54088b0bd3ebae"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -92,7 +92,7 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      " `prj_fits` implements some methods from the [AstroPy `HDUList`](http://astropy.readthedocs.org/en/latest/io/fits/api/hdulists.html) class. `info` shows us the contents of the virtual FITS file:"
+      "Because `FITSImageData` inherits from the [AstroPy `HDUList`](http://astropy.readthedocs.org/en/latest/io/fits/api/hdulists.html) class, we can call its methods. For example, `info` shows us the contents of the virtual FITS file:"
      ]
     },
     {
@@ -109,14 +109,14 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "We can also look at the header for a particular field, using `get_header`:"
+      "We can also look at the header for a particular field:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "prj_fits.get_header(\"temperature\")"
+      "prj_fits[\"temperature\"].header"
      ],
      "language": "python",
      "metadata": {},
@@ -126,7 +126,24 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "where we can see that the temperature units are in Kelvin and the cell widths are in kiloparsecs. We can use the `set_unit` method to change the units of a particular field:"
+      "where we can see that the temperature units are in Kelvin and the cell widths are in kiloparsecs. If we want the raw image data with units, we can call `get_data`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.get_data(\"temperature\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "We can use the `set_unit` method to change the units of a particular field:"
      ]
     },
     {
@@ -134,7 +151,7 @@
      "collapsed": false,
      "input": [
       "prj_fits.set_unit(\"temperature\",\"R\")\n",
-      "print prj_fits[\"temperature\"]"
+      "prj_fits.get_data(\"temperature\")"
      ],
      "language": "python",
      "metadata": {},
@@ -343,14 +360,14 @@
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "By the default, a tangent RA/Dec projection is used, but one could also use another projection using the `ctype` keyword. We can now look at the header and see it has the appropriate WCS now:"
+      "By the default, a tangent RA/Dec projection is used, but one could also use another projection using the `ctype` keyword. We can now look at the header and see it has the appropriate WCS:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "prj_fits.get_header(\"temperature\")"
+      "prj_fits[\"temperature\"].header"
      ],
      "language": "python",
      "metadata": {},
@@ -378,8 +395,8 @@
      "cell_type": "code",
      "collapsed": false,
      "input": [
-      "print fid_frb.get_header(\"density\")[\"time\"]\n",
-      "print fid_frb.get_header(\"temperature\")[\"scale\"]"
+      "print fid_frb[\"density\"].header[\"time\"]\n",
+      "print fid_frb[\"temperature\"].header[\"scale\"]"
      ],
      "language": "python",
      "metadata": {},


https://bitbucket.org/yt_analysis/yt/commits/fbbc537ec75c/
Changeset:   fbbc537ec75c
Branch:      yt
User:        jzuhone
Date:        2015-05-29 05:40:04+00:00
Summary:     Sanity check against tuple field keys
Affected #:  1 file

diff -r e05cffc36d9812ba53fbfbc3bb5445929f1a3587 -r fbbc537ec75c619b0351f339231f964d7e80262b yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -110,7 +110,12 @@
                 fn = fields[0]
             img_data = {fn: data}
 
-        self.fields = fields
+        self.fields = []
+        for fd in fields:
+            if isinstance(fd, tuple):
+                self.fields.append(fd[1])
+            else:
+                self.fields.append(fd)
 
         first = True
         self.field_units = {}


https://bitbucket.org/yt_analysis/yt/commits/696a6134f3f0/
Changeset:   696a6134f3f0
Branch:      yt
User:        jzuhone
Date:        2015-05-29 13:07:45+00:00
Summary:     Bugfix
Affected #:  1 file

diff -r fbbc537ec75c619b0351f339231f964d7e80262b -r 696a6134f3f070d4b55fcfc4c2554db563aab11e yt/analysis_modules/ppv_cube/ppv_cube.py
--- a/yt/analysis_modules/ppv_cube/ppv_cube.py
+++ b/yt/analysis_modules/ppv_cube/ppv_cube.py
@@ -171,7 +171,7 @@
         _vlos = create_vlos(normal, self.no_shifting)
         self.ds.add_field(("gas","v_los"), function=_vlos, units="cm/s")
 
-        _intensity = self.create_intensity()
+        _intensity = self._create_intensity()
         self.ds.add_field(("gas","intensity"), function=_intensity, units=self.field_units)
 
         if method == "integrate" and weight_field is None:


https://bitbucket.org/yt_analysis/yt/commits/16985637841f/
Changeset:   16985637841f
Branch:      yt
User:        jzuhone
Date:        2015-05-29 19:45:01+00:00
Summary:     Merge
Affected #:  29 files

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 .hgignore
--- a/.hgignore
+++ b/.hgignore
@@ -13,6 +13,7 @@
 yt/frontends/ramses/_ramses_reader.cpp
 yt/geometry/fake_octree.c
 yt/geometry/grid_container.c
+yt/geometry/grid_visitors.c
 yt/geometry/oct_container.c
 yt/geometry/oct_visitors.c
 yt/geometry/particle_deposit.c
@@ -25,6 +26,7 @@
 yt/utilities/spatial/ckdtree.c
 yt/utilities/lib/alt_ray_tracers.c
 yt/utilities/lib/amr_kdtools.c
+yt/utilities/lib/bitarray.c
 yt/utilities/lib/CICDeposit.c
 yt/utilities/lib/ContourFinding.c
 yt/utilities/lib/DepthFirstOctree.c
@@ -39,6 +41,7 @@
 yt/utilities/lib/misc_utilities.c
 yt/utilities/lib/Octree.c
 yt/utilities/lib/origami.c
+yt/utilities/lib/pixelization_routines.c
 yt/utilities/lib/png_writer.c
 yt/utilities/lib/PointsInVolume.c
 yt/utilities/lib/QuadTree.c
@@ -59,3 +62,4 @@
 doc/source/reference/api/generated/*
 doc/_temp/*
 doc/source/bootcamp/.ipynb_checkpoints/
+dist

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 .python-version
--- /dev/null
+++ b/.python-version
@@ -0,0 +1,1 @@
+2.7.9

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 README
--- a/README
+++ b/README
@@ -20,4 +20,4 @@
 For more information on installation, what to do if you run into problems, or 
 ways to help development, please visit our website.
 
-Enjoy!
+Enjoy!
\ No newline at end of file

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 doc/source/analyzing/analysis_modules/halo_finders.rst
--- a/doc/source/analyzing/analysis_modules/halo_finders.rst
+++ b/doc/source/analyzing/analysis_modules/halo_finders.rst
@@ -116,7 +116,7 @@
   the width of the smallest grid element in the simulation from the
   last data snapshot (i.e. the one where time has evolved the
   longest) in the time series:
-  ``ds_last.index.get_smallest_dx() * ds_last['mpch']``.
+  ``ds_last.index.get_smallest_dx() * ds_last['Mpch']``.
 * ``total_particles``, if supplied, this is a pre-calculated
   total number of dark matter
   particles present in the simulation. For example, this is useful

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 doc/source/analyzing/time_series_analysis.rst
--- a/doc/source/analyzing/time_series_analysis.rst
+++ b/doc/source/analyzing/time_series_analysis.rst
@@ -79,9 +79,7 @@
 Analyzing an Entire Simulation
 ------------------------------
 
-.. note:: Currently only implemented for Enzo.  Other simulation types coming 
-   soon.  Until then, rely on the above prescription for creating 
-   ``DatasetSeries`` objects.
+.. note:: Implemented for: Enzo, Gadget, OWLS.
 
 The parameter file used to run a simulation contains all the information 
 necessary to know what datasets should be available.  The ``simulation`` 
@@ -93,8 +91,7 @@
 .. code-block:: python
 
   import yt
-  my_sim = yt.simulation('enzo_tiny_cosmology/32Mpc_32.enzo', 'Enzo',
-                         find_outputs=False)
+  my_sim = yt.simulation('enzo_tiny_cosmology/32Mpc_32.enzo', 'Enzo')
 
 Then, create a ``DatasetSeries`` object with the 
 :meth:`frontends.enzo.simulation_handling.EnzoSimulation.get_time_series` 
@@ -123,10 +120,10 @@
 to select a subset of the total data:
 
 * ``time_data`` (*bool*): Whether or not to include time outputs when 
-  gathering datasets for time series.  Default: True.
+  gathering datasets for time series.  Default: True.  (Enzo only)
 
 * ``redshift_data`` (*bool*): Whether or not to include redshift outputs 
-  when gathering datasets for time series.  Default: True.
+  when gathering datasets for time series.  Default: True.  (Enzo only)
 
 * ``initial_time`` (*float*): The earliest time for outputs to be included.  
   If None, the initial time of the simulation is used.  This can be used in 
@@ -139,15 +136,12 @@
 * ``times`` (*list*): A list of times for which outputs will be found.
   Default: None.
 
-* ``time_units`` (*str*): The time units used for requesting outputs by time.
-  Default: '1' (code units).
-
 * ``initial_redshift`` (*float*): The earliest redshift for outputs to be 
   included.  If None, the initial redshift of the simulation is used.  This
   can be used in combination with either ``final_time`` or ``final_redshift``.
   Default: None.
 
-* ``final_time`` (*float*): The latest redshift for outputs to be included.  
+* ``final_redshift`` (*float*): The latest redshift for outputs to be included.  
   If None, the final redshift of the simulation is used.  This can be used 
   in combination with either ``initial_time`` or ``initial_redshift``.  
   Default: None.
@@ -157,11 +151,11 @@
 
 * ``initial_cycle`` (*float*): The earliest cycle for outputs to be 
   included.  If None, the initial cycle of the simulation is used.  This can
-  only be used with final_cycle.  Default: None.
+  only be used with final_cycle.  Default: None.  (Enzo only)
 
 * ``final_cycle`` (*float*): The latest cycle for outputs to be included.  
   If None, the final cycle of the simulation is used.  This can only be used 
-  in combination with initial_cycle.  Default: None.
+  in combination with initial_cycle.  Default: None.  (Enzo only)
 
 * ``tolerance`` (*float*):  Used in combination with ``times`` or ``redshifts`` 
   keywords, this is the tolerance within which outputs are accepted given 

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 doc/source/examining/loading_data.rst
--- a/doc/source/examining/loading_data.rst
+++ b/doc/source/examining/loading_data.rst
@@ -469,6 +469,8 @@
   first image in the primary file. If this is not the case,
   yt will raise a warning and will not load this field.
 
+.. _additional_fits_options:
+
 Additional Options
 ^^^^^^^^^^^^^^^^^^
 
@@ -570,6 +572,35 @@
 ``WCSAxes`` is still in an experimental state, but as its functionality improves it will be
 utilized more here.
 
+``create_spectral_slabs``
+"""""""""""""""""""""""""
+
+.. note::
+
+  The following functionality requires the `spectral-cube <http://spectral-cube.readthedocs.org>`_
+  library to be installed. 
+  
+If you have a spectral intensity dataset of some sort, and would like to extract emission in 
+particular slabs along the spectral axis of a certain width, ``create_spectral_slabs`` can be
+used to generate a dataset with these slabs as different fields. In this example, we use it
+to extract individual lines from an intensity cube:
+
+.. code-block:: python
+
+  slab_centers = {'13CN': (218.03117, 'GHz'),
+                  'CH3CH2CHO': (218.284256, 'GHz'),
+                  'CH3NH2': (218.40956, 'GHz')}
+  slab_width = (0.05, "GHz")
+  ds = create_spectral_slabs("intensity_cube.fits",
+                                    slab_centers, slab_width,
+                                    nan_mask=0.0)
+
+All keyword arguments to `create_spectral_slabs` are passed on to `load` when creating the dataset
+(see :ref:`additional_fits_options` above). In the returned dataset, the different slabs will be
+different fields, with the field names taken from the keys in ``slab_centers``. The WCS coordinates 
+on the spectral axis are reset so that the center of the domain along this axis is zero, and the 
+left and right edges of the domain along this axis are :math:`\pm` ``0.5*slab_width``.
+
 Examples of Using FITS Data
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -635,13 +666,14 @@
    import yt
    ds = yt.load("snapshot_061.hdf5")
 
-However, yt cannot detect raw-binary Gadget data, and so you must specify the
-format as being Gadget:
+Gadget data in raw binary format can also be loaded with the ``load`` command. 
+This is only supported for snapshots created with the ``SnapFormat`` parameter 
+set to 1 (the standard for Gadget-2).
 
 .. code-block:: python
 
    import yt
-   ds = yt.GadgetDataset("snapshot_061")
+   ds = yt.load("snapshot_061")
 
 .. _particle-bbox:
 

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 doc/source/installing.rst
--- a/doc/source/installing.rst
+++ b/doc/source/installing.rst
@@ -213,10 +213,31 @@
 ++++++++++++++++++++++++++++++++++++++
 
 To install yt from source, you must make sure you have yt's dependencies
-installed on your system.  These include: a C compiler, ``HDF5``, ``python``,
-``Cython``, ``NumPy``, ``matplotlib``, ``sympy``, and ``h5py``. From here, you
-can use ``pip`` (which comes with ``Python``) to install the latest stable
-version of yt:
+installed on your system. 
+
+If you use a Linux OS, use your distro's package manager to install these yt
+dependencies on your system:
+
+- ``HDF5``
+- ``zeromq``
+- ``sqlite`` 
+- ``mercurial``
+
+Then install the required Python packages with ``pip``:
+
+.. code-block:: bash
+
+  $ pip install -r requirements.txt
+
+If you're using IPython notebooks, you can install its dependencies
+with ``pip`` as well:
+
+.. code-block:: bash
+
+  $ pip install -r optional-requirements.txt
+
+From here, you can use ``pip`` (which comes with ``Python``) to install the latest
+stable version of yt:
 
 .. code-block:: bash
 

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 doc/source/visualizing/sketchfab.rst
--- a/doc/source/visualizing/sketchfab.rst
+++ b/doc/source/visualizing/sketchfab.rst
@@ -56,7 +56,7 @@
 
    import yt
    ds = yt.load("/data/workshop2012/IsolatedGalaxy/galaxy0030/galaxy0030")
-   sphere = ds.sphere("max", (1.0, "mpc"))
+   sphere = ds.sphere("max", (1.0, "Mpc"))
    surface = ds.surface(sphere, "density", 1e-27)
 
 This object, ``surface``, can be queried for values on the surface.  For
@@ -172,7 +172,7 @@
    trans = [1.0, 0.5]
    filename = './surfaces'
 
-   sphere = ds.sphere("max", (1.0, "mpc"))
+   sphere = ds.sphere("max", (1.0, "Mpc"))
    for i,r in enumerate(rho):
        surf = ds.surface(sphere, 'density', r)
        surf.export_obj(filename, transparency = trans[i], color_field='temperature', plot_index = i)
@@ -248,7 +248,7 @@
        return (data['density']*data['density']*np.sqrt(data['temperature']))
    add_field("emissivity", function=_Emissivity, units=r"g*K/cm**6")
 
-   sphere = ds.sphere("max", (1.0, "mpc"))
+   sphere = ds.sphere("max", (1.0, "Mpc"))
    for i,r in enumerate(rho):
        surf = ds.surface(sphere, 'density', r)
        surf.export_obj(filename, transparency = trans[i],

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 optional-requirements.txt
--- /dev/null
+++ b/optional-requirements.txt
@@ -0,0 +1,1 @@
+ipython[notebook]
\ No newline at end of file

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 requirements.txt
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,6 @@
+numpy==1.9.2 
+matplotlib==1.4.3 
+Cython==0.22 
+h5py==2.5.0 
+nose==1.3.6 
+sympy==0.7.6 

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/analysis_modules/absorption_spectrum/absorption_spectrum.py
--- a/yt/analysis_modules/absorption_spectrum/absorption_spectrum.py
+++ b/yt/analysis_modules/absorption_spectrum/absorption_spectrum.py
@@ -127,8 +127,8 @@
         field_units = {"dl": "cm", "redshift": "", "temperature": "K"}
         field_data = {}
         if use_peculiar_velocity:
-            input_fields.append('los_velocity')
-            field_units["los_velocity"] = "cm/s"
+            input_fields.append('velocity_los')
+            field_units["velocity_los"] = "cm/s"
         for feature in self.line_list + self.continuum_list:
             if not feature['field_name'] in input_fields:
                 input_fields.append(feature['field_name'])
@@ -171,7 +171,7 @@
             if use_peculiar_velocity:
                 # include factor of (1 + z) because our velocity is in proper frame.
                 delta_lambda += continuum['wavelength'] * (1 + field_data['redshift']) * \
-                    field_data['los_velocity'] / speed_of_light_cgs
+                    field_data['velocity_los'] / speed_of_light_cgs
             this_wavelength = delta_lambda + continuum['wavelength']
             right_index = np.digitize(this_wavelength, self.lambda_bins).clip(0, self.n_lambda)
             left_index = np.digitize((this_wavelength *
@@ -208,7 +208,7 @@
             if use_peculiar_velocity:
                 # include factor of (1 + z) because our velocity is in proper frame.
                 delta_lambda += line['wavelength'] * (1 + field_data['redshift']) * \
-                    field_data['los_velocity'] / speed_of_light_cgs
+                    field_data['velocity_los'] / speed_of_light_cgs
             thermal_b = km_per_cm * np.sqrt((2 * boltzmann_constant_cgs *
                                              field_data['temperature']) /
                                             (amu_cgs * line['atomic_mass']))
@@ -260,7 +260,7 @@
                 if line['label_threshold'] is not None and \
                         column_density[lixel] >= line['label_threshold']:
                     if use_peculiar_velocity:
-                        peculiar_velocity = km_per_cm * field_data['los_velocity'][lixel]
+                        peculiar_velocity = km_per_cm * field_data['velocity_los'][lixel]
                     else:
                         peculiar_velocity = 0.0
                     self.spectrum_line_list.append({'label': line['label'],

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/analysis_modules/cosmological_observation/light_ray/light_ray.py
--- a/yt/analysis_modules/cosmological_observation/light_ray/light_ray.py
+++ b/yt/analysis_modules/cosmological_observation/light_ray/light_ray.py
@@ -33,6 +33,13 @@
 
 class LightRay(CosmologySplice):
     """
+    LightRay(parameter_filename, simulation_type=None,
+             near_redshift=None, far_redshift=None,
+             use_minimum_datasets=True, deltaz_min=0.0,
+             minimum_coherent_box_fraction=0.0,
+             time_data=True, redshift_data=True,
+             find_outputs=False, load_kwargs=None):
+
     Create a LightRay object.  A light ray is much like a light cone,
     in that it stacks together multiple datasets in order to extend a
     redshift interval.  Unlike a light cone, which does randomly
@@ -94,6 +101,12 @@
         Whether or not to search for datasets in the current 
         directory.
         Default: False.
+    load_kwargs : optional, dict
+        Optional dictionary of kwargs to be passed to the "load" 
+        function, appropriate for use of certain frontends.  E.g.
+        Tipsy using "bounding_box"
+        Gadget using "unit_base", etc.
+        Default : None
 
     """
     def __init__(self, parameter_filename, simulation_type=None,
@@ -101,7 +114,7 @@
                  use_minimum_datasets=True, deltaz_min=0.0,
                  minimum_coherent_box_fraction=0.0,
                  time_data=True, redshift_data=True,
-                 find_outputs=False):
+                 find_outputs=False, load_kwargs=None):
 
         self.near_redshift = near_redshift
         self.far_redshift = far_redshift
@@ -109,13 +122,16 @@
         self.deltaz_min = deltaz_min
         self.minimum_coherent_box_fraction = minimum_coherent_box_fraction
         self.parameter_filename = parameter_filename
-
+        if load_kwargs is None:
+            self.load_kwargs = {}
+        else:
+            self.load_kwargs = load_kwargs
         self.light_ray_solution = []
         self._data = {}
 
         # Make a light ray from a single, given dataset.        
         if simulation_type is None:
-            ds = load(parameter_filename)
+            ds = load(parameter_filename, **self.load_kwargs)
             if ds.cosmological_simulation:
                 redshift = ds.current_redshift
                 self.cosmology = Cosmology(
@@ -243,6 +259,12 @@
                        get_los_velocity=True, redshift=None,
                        njobs=-1):
         """
+        make_light_ray(seed=None, start_position=None, end_position=None,
+                       trajectory=None, fields=None, setup_function=None,
+                       solution_filename=None, data_filename=None,
+                       get_los_velocity=True, redshift=None,
+                       njobs=-1)
+
         Create a light ray and get field values for each lixel.  A light
         ray consists of a list of field values for cells intersected by
         the ray and the path length of the ray through those cells.
@@ -343,9 +365,9 @@
         all_fields = fields[:]
         all_fields.extend(['dl', 'dredshift', 'redshift'])
         if get_los_velocity:
-            all_fields.extend(['x-velocity', 'y-velocity',
-                               'z-velocity', 'los_velocity'])
-            data_fields.extend(['x-velocity', 'y-velocity', 'z-velocity'])
+            all_fields.extend(['velocity_x', 'velocity_y',
+                               'velocity_z', 'velocity_los'])
+            data_fields.extend(['velocity_x', 'velocity_y', 'velocity_z'])
 
         all_ray_storage = {}
         for my_storage, my_segment in parallel_objects(self.light_ray_solution,
@@ -353,7 +375,7 @@
                                                        njobs=njobs):
 
             # Load dataset for segment.
-            ds = load(my_segment['filename'])
+            ds = load(my_segment['filename'], **self.load_kwargs)
 
             my_segment['unique_identifier'] = ds.unique_identifier
             if redshift is not None:
@@ -364,11 +386,15 @@
 
             if setup_function is not None:
                 setup_function(ds)
-            
-            my_segment["start"] = ds.domain_width * my_segment["start"] + \
-                ds.domain_left_edge
-            my_segment["end"] = ds.domain_width * my_segment["end"] + \
-                ds.domain_left_edge
+
+            if start_position is not None:
+                my_segment["start"] = ds.arr(my_segment["start"], "code_length")
+                my_segment["end"] = ds.arr(my_segment["end"], "code_length")
+            else:
+                my_segment["start"] = ds.domain_width * my_segment["start"] + \
+                  ds.domain_left_edge
+                my_segment["end"] = ds.domain_width * my_segment["end"] + \
+                  ds.domain_left_edge
 
             if not ds.cosmological_simulation:
                 next_redshift = my_segment["redshift"]
@@ -412,10 +438,10 @@
                 if get_los_velocity:
                     line_of_sight = sub_segment[1] - sub_segment[0]
                     line_of_sight /= ((line_of_sight**2).sum())**0.5
-                    sub_vel = ds.arr([sub_ray['x-velocity'],
-                                      sub_ray['y-velocity'],
-                                      sub_ray['z-velocity']])
-                    sub_data['los_velocity'].extend((np.rollaxis(sub_vel, 1) *
+                    sub_vel = ds.arr([sub_ray['velocity_x'],
+                                      sub_ray['velocity_y'],
+                                      sub_ray['velocity_z']])
+                    sub_data['velocity_los'].extend((np.rollaxis(sub_vel, 1) *
                                                      line_of_sight).sum(axis=1)[asort])
                     del sub_vel
 
@@ -423,7 +449,6 @@
                 del sub_ray, asort
 
             for key in sub_data:
-                if key in "xyz": continue
                 sub_data[key] = ds.arr(sub_data[key]).in_cgs()
 
             # Get redshift for each lixel.  Assume linear relation between l and z.
@@ -461,18 +486,32 @@
 
     @parallel_root_only
     def _write_light_ray(self, filename, data):
-        "Write light ray data to hdf5 file."
+        """
+        _write_light_ray(filename, data)
+
+        Write light ray data to hdf5 file.
+        """
 
         mylog.info("Saving light ray data to %s." % filename)
         output = h5py.File(filename, 'w')
         for field in data.keys():
-            output.create_dataset(field, data=data[field])
-            output[field].attrs["units"] = str(data[field].units)
+            # if the field is a tuple, only use the second part of the tuple
+            # in the hdf5 output (i.e. ('gas', 'density') -> 'density')
+            if isinstance(field, tuple):
+                fieldname = field[1]
+            else:
+                fieldname = field
+            output.create_dataset(fieldname, data=data[field])
+            output[fieldname].attrs["units"] = str(data[field].units)
         output.close()
 
     @parallel_root_only
     def _write_light_ray_solution(self, filename, extra_info=None):
-        "Write light ray solution to a file."
+        """
+        _write_light_ray_solution(filename, extra_info=None)
+
+        Write light ray solution to a file.
+        """
 
         mylog.info("Writing light ray solution to %s." % filename)
         f = open(filename, 'w')
@@ -490,7 +529,11 @@
         f.close()
 
 def _flatten_dict_list(data, exceptions=None):
-    "Flatten the list of dicts into one dict."
+    """
+    _flatten_dict_list(data, exceptions=None)
+
+    Flatten the list of dicts into one dict.
+    """
 
     if exceptions is None: exceptions = []
     new_data = {}
@@ -505,12 +548,20 @@
     return new_data
 
 def vector_length(start, end):
-    "Calculate vector length."
+    """
+    vector_length(start, end)
+    
+    Calculate vector length.
+    """
 
     return np.sqrt(np.power((end - start), 2).sum())
 
 def periodic_distance(coord1, coord2):
-    "Calculate length of shortest vector between to points in periodic domain."
+    """
+    periodic_distance(coord1, coord2)
+
+    Calculate length of shortest vector between to points in periodic domain.
+    """
     dif = coord1 - coord2
 
     dim = np.ones(coord1.shape,dtype=int)
@@ -524,6 +575,8 @@
 
 def periodic_ray(start, end, left=None, right=None):
     """
+    periodic_ray(start, end, left=None, right=None)
+
     Break up periodic ray into non-periodic segments. 
     Accepts start and end points of periodic ray as YTArrays.
     Accepts optional left and right edges of periodic volume as YTArrays.

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/analysis_modules/halo_finding/halo_objects.py
--- a/yt/analysis_modules/halo_finding/halo_objects.py
+++ b/yt/analysis_modules/halo_finding/halo_objects.py
@@ -1232,9 +1232,8 @@
         fglob = path.join(basedir, 'halos_%d.*.bin' % n)
         files = glob.glob(fglob)
         halos = self._get_halos_binary(files)
-        #Jc = mass_sun_cgs/ ds['mpchcm'] * 1e5
         Jc = 1.0
-        length = 1.0 / ds['mpchcm']
+        length = 1.0 / ds['Mpchcm']
         conv = dict(pos = np.array([length, length, length,
                                     1, 1, 1]), # to unitary
                     r=1.0/ds['kpchcm'], # to unitary

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/data_objects/selection_data_containers.py
--- a/yt/data_objects/selection_data_containers.py
+++ b/yt/data_objects/selection_data_containers.py
@@ -729,7 +729,7 @@
 
     >>> import yt
     >>> ds = yt.load("RedshiftOutput0005")
-    >>> sp = ds.sphere("max", (1.0, 'mpc'))
+    >>> sp = ds.sphere("max", (1.0, 'Mpc'))
     >>> cr = ds.cut_region(sp, ["obj['temperature'] < 1e3"])
     """
     _type_name = "cut_region"

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/data_objects/time_series.py
--- a/yt/data_objects/time_series.py
+++ b/yt/data_objects/time_series.py
@@ -406,6 +406,7 @@
         self.basename = os.path.basename(parameter_filename)
         self.directory = os.path.dirname(parameter_filename)
         self.parameters = {}
+        self.key_parameters = []
 
         # Set some parameter defaults.
         self._set_parameter_defaults()
@@ -420,6 +421,21 @@
         
         self.print_key_parameters()
 
+    def _set_parameter_defaults(self):
+        pass
+
+    def _parse_parameter_file(self):
+        pass
+
+    def _set_units(self):
+        pass
+
+    def _calculate_simulation_bounds(self):
+        pass
+
+    def _get_all_outputs(**kwargs):
+        pass
+        
     def __repr__(self):
         return self.parameter_filename
 
@@ -445,23 +461,78 @@
         """
         Print out some key parameters for the simulation.
         """
-        for a in ["domain_dimensions", "domain_left_edge",
-                  "domain_right_edge", "initial_time", "final_time",
-                  "stop_cycle", "cosmological_simulation"]:
-            if not hasattr(self, a):
-                mylog.error("Missing %s in dataset definition!", a)
-                continue
-            v = getattr(self, a)
-            mylog.info("Parameters: %-25s = %s", a, v)
-        if hasattr(self, "cosmological_simulation") and \
-           getattr(self, "cosmological_simulation"):
+        if self.simulation_type == "grid":
+            for a in ["domain_dimensions", "domain_left_edge",
+                      "domain_right_edge"]:
+                self._print_attr(a)
+        for a in ["initial_time", "final_time",
+                  "cosmological_simulation"]:
+            self._print_attr(a)
+        if getattr(self, "cosmological_simulation", False):
             for a in ["box_size", "omega_lambda",
                       "omega_matter", "hubble_constant",
                       "initial_redshift", "final_redshift"]:
-                if not hasattr(self, a):
-                    mylog.error("Missing %s in dataset definition!", a)
-                    continue
-                v = getattr(self, a)
-                mylog.info("Parameters: %-25s = %s", a, v)
+                self._print_attr(a)
+        for a in self.key_parameters:
+            self._print_attr(a)
         mylog.info("Total datasets: %d." % len(self.all_outputs))
 
+    def _print_attr(self, a):
+        """
+        Print the attribute or warn about it missing.
+        """
+        if not hasattr(self, a):
+            mylog.error("Missing %s in dataset definition!", a)
+            return
+        v = getattr(self, a)
+        mylog.info("Parameters: %-25s = %s", a, v)
+
+    def _get_outputs_by_key(self, key, values, tolerance=None, outputs=None):
+        r"""
+        Get datasets at or near to given values.
+
+        Parameters
+        ----------
+        key: str
+            The key by which to retrieve outputs, usually 'time' or
+            'redshift'.
+        values: array_like
+            A list of values, given as floats.
+        tolerance : float
+            If not None, do not return a dataset unless the value is
+            within the tolerance value.  If None, simply return the
+            nearest dataset.
+            Default: None.
+        outputs : list
+            The list of outputs from which to choose.  If None,
+            self.all_outputs is used.
+            Default: None.
+
+        Examples
+        --------
+        >>> datasets = es.get_outputs_by_key('redshift', [0, 1, 2], tolerance=0.1)
+
+        """
+
+        if not isinstance(values, YTArray):
+            if isinstance(values, tuple) and len(values) == 2:
+                values = self.arr(*values)
+            else:
+                values = self.arr(values)
+        values = values.in_cgs()
+
+        if outputs is None:
+            outputs = self.all_outputs
+        my_outputs = []
+        if not outputs:
+            return my_outputs
+        for value in values:
+            outputs.sort(key=lambda obj:np.abs(value - obj[key]))
+            if (tolerance is None or np.abs(value - outputs[0][key]) <= tolerance) \
+                    and outputs[0] not in my_outputs:
+                my_outputs.append(outputs[0])
+            else:
+                mylog.error("No dataset added for %s = %f.", key, value)
+
+        outputs.sort(key=lambda obj: obj['time'])
+        return my_outputs

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/fields/field_aliases.py
--- a/yt/fields/field_aliases.py
+++ b/yt/fields/field_aliases.py
@@ -141,12 +141,12 @@
     ("CellMassCode",                          "code_mass"),
     ("TotalMassMsun",                         "msun"),
     ("CellVolumeCode",                        "code_length"),
-    ("CellVolumeMpc",                         "mpc**3"),
-    ("ParticleSpecificAngularMomentumXKMSMPC","km/s/mpc"),
-    ("ParticleSpecificAngularMomentumYKMSMPC","km/s/mpc"),
-    ("ParticleSpecificAngularMomentumZKMSMPC","km/s/mpc"),
-    ("RadiusMpc",                             "mpc"),
-    ("ParticleRadiusMpc",                     "mpc"),
+    ("CellVolumeMpc",                         "Mpc**3"),
+    ("ParticleSpecificAngularMomentumXKMSMPC","km/s/Mpc"),
+    ("ParticleSpecificAngularMomentumYKMSMPC","km/s/Mpc"),
+    ("ParticleSpecificAngularMomentumZKMSMPC","km/s/Mpc"),
+    ("RadiusMpc",                             "Mpc"),
+    ("ParticleRadiusMpc",                     "Mpc"),
     ("ParticleRadiuskpc",                     "kpc"),
     ("Radiuskpc",                             "kpc"),
     ("ParticleRadiuskpch",                    "kpc"),

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/enzo/data_structures.py
--- a/yt/frontends/enzo/data_structures.py
+++ b/yt/frontends/enzo/data_structures.py
@@ -890,7 +890,7 @@
         elif self.dimensionality == 2:
             self._setup_2d()
 
-    def set_code_units(self):
+    def _set_code_unit_attributes(self):
         if self.cosmological_simulation:
             k = self.cosmology_get_units()
             # Now some CGS values
@@ -928,17 +928,6 @@
         magnetic_unit = np.float64(magnetic_unit.in_cgs())
         self.magnetic_unit = self.quan(magnetic_unit, "gauss")
 
-        self._override_code_units()
-
-        self.unit_registry.modify("code_magnetic", self.magnetic_unit)
-        self.unit_registry.modify("code_length", self.length_unit)
-        self.unit_registry.modify("code_mass", self.mass_unit)
-        self.unit_registry.modify("code_time", self.time_unit)
-        self.unit_registry.modify("code_velocity", self.velocity_unit)
-        DW = self.arr(self.domain_right_edge - self.domain_left_edge, "code_length")
-        self.unit_registry.add("unitary", float(DW.max() * DW.units.base_value),
-                               DW.units.dimensions)
-
     def cosmology_get_units(self):
         """
         Return an Enzo-fortran style dictionary of units to feed into custom

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/enzo/simulation_handling.py
--- a/yt/frontends/enzo/simulation_handling.py
+++ b/yt/frontends/enzo/simulation_handling.py
@@ -13,36 +13,34 @@
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
-from yt.funcs import *
-
 import numpy as np
 import glob
 import os
 
 from yt.convenience import \
-    load
+    load, \
+    only_on_root
 from yt.data_objects.time_series import \
     SimulationTimeSeries, DatasetSeries
 from yt.units import dimensions
 from yt.units.unit_registry import \
-     UnitRegistry
+    UnitRegistry
 from yt.units.yt_array import \
-     YTArray, YTQuantity
+    YTArray, YTQuantity
 from yt.utilities.cosmology import \
     Cosmology
-from yt.utilities.definitions import \
-    sec_conversion
 from yt.utilities.exceptions import \
     InvalidSimulationTimeSeries, \
     MissingParameter, \
     NoStoppingCondition
+from yt.utilities.logger import ytLogger as \
+    mylog
 from yt.utilities.parallel_tools.parallel_analysis_interface import \
     parallel_objects
-from yt.utilities.physical_constants import \
-    gravitational_constant_cgs as G
-
+    
 class EnzoSimulation(SimulationTimeSeries):
-    r"""Initialize an Enzo Simulation object.
+    r"""
+    Initialize an Enzo Simulation object.
 
     Upon creation, the parameter file is parsed and the time and redshift
     are calculated and stored in all_outputs.  A time units dictionary is
@@ -63,14 +61,8 @@
 
     Examples
     --------
-    >>> from yt.mods import *
-    >>> es = EnzoSimulation("my_simulation.par")
-    >>> es.get_time_series()
-    >>> for ds in es:
-    ...     print ds.current_time
-
-    >>> from yt.mods import *
-    >>> es = simulation("my_simulation.par", "Enzo")
+    >>> import yt
+    >>> es = yt.simulation("my_simulation.par", "Enzo")
     >>> es.get_time_series()
     >>> for ds in es:
     ...     print ds.current_time
@@ -78,7 +70,8 @@
     """
 
     def __init__(self, parameter_filename, find_outputs=False):
-
+        self.simulation_type = "grid"
+        self.key_parameters = ["stop_cycle"]
         SimulationTimeSeries.__init__(self, parameter_filename,
                                       find_outputs=find_outputs)
 
@@ -87,14 +80,14 @@
         self.unit_registry.lut["code_time"] = (1.0, dimensions.time)
         if self.cosmological_simulation:
             # Instantiate EnzoCosmology object for units and time conversions.
-            self.enzo_cosmology = \
+            self.cosmology = \
               EnzoCosmology(self.parameters['CosmologyHubbleConstantNow'],
                             self.parameters['CosmologyOmegaMatterNow'],
                             self.parameters['CosmologyOmegaLambdaNow'],
                             0.0, self.parameters['CosmologyInitialRedshift'],
                             unit_registry=self.unit_registry)
 
-            self.time_unit = self.enzo_cosmology.time_unit.in_units("s")
+            self.time_unit = self.cosmology.time_unit.in_units("s")
             self.unit_registry.modify("h", self.hubble_constant)
             # Comoving lengths
             for my_unit in ["m", "pc", "AU", "au"]:
@@ -160,7 +153,7 @@
             used in combination with either final_time or
             final_redshift.
             Default: None.
-        final_time : float
+        final_redshift : float
             The latest redshift for outputs to be included.  If None,
             the final redshift of the simulation is used.  This can be
             used in combination with either initial_time or
@@ -197,8 +190,8 @@
         Examples
         --------
 
-        >>> from yt.mods import *
-        >>> es = simulation("my_simulation.par", "Enzo")
+        >>> import yt
+        >>> es = yt.simulation("my_simulation.par", "Enzo")
         
         >>> es.get_time_series(initial_redshift=10, final_time=(13.7, "Gyr"), 
                                redshift_data=False)
@@ -207,8 +200,6 @@
 
         >>> es.get_time_series(final_cycle=100000)
 
-        >>> es.get_time_series(find_outputs=True)
-
         >>> # after calling get_time_series
         >>> for ds in es.piter():
         ...     p = ProjectionPlot(ds, 'x', "density")
@@ -226,7 +217,9 @@
         if (initial_redshift is not None or \
             final_redshift is not None) and \
             not self.cosmological_simulation:
-            raise InvalidSimulationTimeSeries('An initial or final redshift has been given for a noncosmological simulation.')
+            raise InvalidSimulationTimeSeries(
+                "An initial or final redshift has been given for a " +
+                "noncosmological simulation.")
 
         if time_data and redshift_data:
             my_all_outputs = self.all_outputs
@@ -244,12 +237,14 @@
 
         # Apply selection criteria to the set.
         if times is not None:
-            my_outputs = self._get_outputs_by_time(times, tolerance=tolerance,
-                                                   outputs=my_all_outputs)
+            my_outputs = self._get_outputs_by_key("time", times,
+                                                  tolerance=tolerance,
+                                                  outputs=my_all_outputs)
 
         elif redshifts is not None:
-            my_outputs = self._get_outputs_by_redshift(redshifts, tolerance=tolerance,
-                                                       outputs=my_all_outputs)
+            my_outputs = self._get_outputs_by_key("redshift", redshifts,
+                                                  tolerance=tolerance,
+                                                  outputs=my_all_outputs)
 
         elif initial_cycle is not None or final_cycle is not None:
             if initial_cycle is None:
@@ -272,9 +267,11 @@
                 elif isinstance(initial_time, tuple) and len(initial_time) == 2:
                     initial_time = self.quan(*initial_time)
                 elif not isinstance(initial_time, YTArray):
-                    raise RuntimeError("Error: initial_time must be given as a float or tuple of (value, units).")
+                    raise RuntimeError(
+                        "Error: initial_time must be given as a float or " +
+                        "tuple of (value, units).")
             elif initial_redshift is not None:
-                my_initial_time = self.enzo_cosmology.t_from_z(initial_redshift)
+                my_initial_time = self.cosmology.t_from_z(initial_redshift)
             else:
                 my_initial_time = self.initial_time
 
@@ -284,10 +281,12 @@
                 elif isinstance(final_time, tuple) and len(final_time) == 2:
                     final_time = self.quan(*final_time)
                 elif not isinstance(final_time, YTArray):
-                    raise RuntimeError("Error: final_time must be given as a float or tuple of (value, units).")
+                    raise RuntimeError(
+                        "Error: final_time must be given as a float or " +
+                        "tuple of (value, units).")
                 my_final_time = final_time.in_units("s")
             elif final_redshift is not None:
-                my_final_time = self.enzo_cosmology.t_from_z(final_redshift)
+                my_final_time = self.cosmology.t_from_z(final_redshift)
             else:
                 my_final_time = self.final_time
 
@@ -390,8 +389,9 @@
                     raise MissingParameter(self.parameter_filename, v)
                 setattr(self, a, self.parameters[v])
         else:
+            self.cosmological_simulation = 0
             self.omega_lambda = self.omega_matter = \
-                self.hubble_constant = self.cosmological_simulation = 0.0
+                self.hubble_constant = 0.0
 
         # make list of redshift outputs
         self.all_redshift_outputs = []
@@ -405,16 +405,10 @@
             del output['index']
         self.all_redshift_outputs = redshift_outputs
 
-    def _calculate_redshift_dump_times(self):
-        "Calculates time from redshift of redshift outputs."
-
-        if not self.cosmological_simulation: return
-        for output in self.all_redshift_outputs:
-            output['time'] = self.enzo_cosmology.t_from_z(output['redshift'])
-        self.all_redshift_outputs.sort(key=lambda obj:obj['time'])
-
     def _calculate_time_outputs(self):
-        "Calculate time outputs and their redshifts if cosmological."
+        """
+        Calculate time outputs and their redshifts if cosmological.
+        """
 
         self.all_time_outputs = []
         if self.final_time is None or \
@@ -432,7 +426,7 @@
             output = {'index': index, 'filename': filename, 'time': current_time.copy()}
             output['time'] = min(output['time'], self.final_time)
             if self.cosmological_simulation:
-                output['redshift'] = self.enzo_cosmology.z_from_t(current_time)
+                output['redshift'] = self.cosmology.z_from_t(current_time)
 
             self.all_time_outputs.append(output)
             if np.abs(self.final_time - current_time) / self.final_time < 1e-4: break
@@ -440,7 +434,9 @@
             index += 1
 
     def _calculate_cycle_outputs(self):
-        "Calculate cycle outputs."
+        """
+        Calculate cycle outputs.
+        """
 
         mylog.warn('Calculating cycle outputs.  Dataset times will be unavailable.')
 
@@ -460,7 +456,9 @@
             index += 1
 
     def _get_all_outputs(self, find_outputs=False):
-        "Get all potential datasets and combine into a time-sorted list."
+        """
+        Get all potential datasets and combine into a time-sorted list.
+        """
 
         # Create the set of outputs from which further selection will be done.
         if find_outputs:
@@ -468,8 +466,12 @@
 
         elif self.parameters['dtDataDump'] > 0 and \
           self.parameters['CycleSkipDataDump'] > 0:
-            mylog.info("Simulation %s has both dtDataDump and CycleSkipDataDump set.", self.parameter_filename )
-            mylog.info("    Unable to calculate datasets.  Attempting to search in the current directory")
+            mylog.info(
+                "Simulation %s has both dtDataDump and CycleSkipDataDump set.",
+                self.parameter_filename )
+            mylog.info(
+                "    Unable to calculate datasets.  " +
+                "Attempting to search in the current directory")
             self._find_outputs()
 
         else:
@@ -480,7 +482,10 @@
                 self._calculate_time_outputs()
 
             # Calculate times for redshift outputs.
-            self._calculate_redshift_dump_times()
+            if self.cosmological_simulation:
+                for output in self.all_redshift_outputs:
+                    output["time"] = self.cosmology.t_from_z(output["redshift"])
+                self.all_redshift_outputs.sort(key=lambda obj:obj["time"])
 
             self.all_outputs = self.all_time_outputs + self.all_redshift_outputs
             if self.parameters['CycleSkipDataDump'] <= 0:
@@ -496,9 +501,9 @@
 
         # Convert initial/final redshifts to times.
         if self.cosmological_simulation:
-            self.initial_time = self.enzo_cosmology.t_from_z(self.initial_redshift)
+            self.initial_time = self.cosmology.t_from_z(self.initial_redshift)
             self.initial_time.units.registry = self.unit_registry
-            self.final_time = self.enzo_cosmology.t_from_z(self.final_redshift)
+            self.final_time = self.cosmology.t_from_z(self.final_redshift)
             self.final_time.units.registry = self.unit_registry
 
         # If not a cosmology simulation, figure out the stopping criteria.
@@ -516,11 +521,15 @@
                     'StopCycle' in self.parameters):
                 raise NoStoppingCondition(self.parameter_filename)
             if self.final_time is None:
-                mylog.warn('Simulation %s has no stop time set, stopping condition will be based only on cycles.',
-                           self.parameter_filename)
+                mylog.warn(
+                    "Simulation %s has no stop time set, stopping condition " +
+                    "will be based only on cycles.",
+                    self.parameter_filename)
 
     def _set_parameter_defaults(self):
-        "Set some default parameters to avoid problems if they are not in the parameter file."
+        """
+        Set some default parameters to avoid problems if they are not in the parameter file.
+        """
 
         self.parameters['GlobalDir'] = self.directory
         self.parameters['DataDumpName'] = "data"
@@ -570,7 +579,9 @@
                 self.final_redshift = self.all_outputs[-1]['redshift']
 
     def _check_for_outputs(self, potential_outputs):
-        r"""Check a list of files to see if they are valid datasets."""
+        """
+        Check a list of files to see if they are valid datasets.
+        """
 
         only_on_root(mylog.info, "Checking %d potential outputs.", 
                      len(potential_outputs))
@@ -603,112 +614,10 @@
 
         return my_outputs
 
-    def _get_outputs_by_key(self, key, values, tolerance=None, outputs=None):
-        r"""Get datasets at or near to given values.
-
-        Parameters
-        ----------
-        key: str
-            The key by which to retrieve outputs, usually 'time' or
-            'redshift'.
-        values: array_like
-            A list of values, given as floats.
-        tolerance : float
-            If not None, do not return a dataset unless the value is
-            within the tolerance value.  If None, simply return the
-            nearest dataset.
-            Default: None.
-        outputs : list
-            The list of outputs from which to choose.  If None,
-            self.all_outputs is used.
-            Default: None.
-
-        Examples
-        --------
-        >>> datasets = es.get_outputs_by_key('redshift', [0, 1, 2], tolerance=0.1)
-
-        """
-
-        if not isinstance(values, np.ndarray):
-            values = ensure_list(values)
-        if outputs is None:
-            outputs = self.all_outputs
-        my_outputs = []
-        if not outputs:
-            return my_outputs
-        for value in values:
-            outputs.sort(key=lambda obj:np.abs(value - obj[key]))
-            if (tolerance is None or np.abs(value - outputs[0][key]) <= tolerance) \
-                    and outputs[0] not in my_outputs:
-                my_outputs.append(outputs[0])
-            else:
-                mylog.error("No dataset added for %s = %f.", key, value)
-
-        outputs.sort(key=lambda obj: obj['time'])
-        return my_outputs
-
-    def _get_outputs_by_redshift(self, redshifts, tolerance=None, outputs=None):
-        r"""Get datasets at or near to given redshifts.
-
-        Parameters
-        ----------
-        redshifts: array_like
-            A list of redshifts, given as floats.
-        tolerance : float
-            If not None, do not return a dataset unless the value is
-            within the tolerance value.  If None, simply return the
-            nearest dataset.
-            Default: None.
-        outputs : list
-            The list of outputs from which to choose.  If None,
-            self.all_outputs is used.
-            Default: None.
-
-        Examples
-        --------
-        >>> datasets = es.get_outputs_by_redshift([0, 1, 2], tolerance=0.1)
-
-        """
-
-        return self._get_outputs_by_key('redshift', redshifts, tolerance=tolerance,
-                                     outputs=outputs)
-
-    def _get_outputs_by_time(self, times, tolerance=None, outputs=None):
-        r"""Get datasets at or near to given times.
-
-        Parameters
-        ----------
-        times: tuple of type (float array, str)
-            A list of times for which outputs will be found and the units 
-            of those values.  For example, ([0, 1, 2, 3], "s").
-        tolerance : float
-            If not None, do not return a dataset unless the time is
-            within the tolerance value.  If None, simply return the
-            nearest dataset.
-            Default = None.
-        outputs : list
-            The list of outputs from which to choose.  If None,
-            self.all_outputs is used.
-            Default: None.
-
-        Examples
-        --------
-        >>> datasets = es.get_outputs_by_time([600, 500, 400], tolerance=10.)
-
-        """
-
-        if not isinstance(times, YTArray):
-            if isinstance(times, tuple) and len(times) == 2:
-                times = self.arr(*times)
-            else:
-                times = self.arr(times, "code_time")
-        times = times.in_units("s")
-        return self._get_outputs_by_key('time', times, tolerance=tolerance,
-                                        outputs=outputs)
-
     def _write_cosmology_outputs(self, filename, outputs, start_index,
                                  decimals=3):
-        r"""Write cosmology output parameters for a cosmology splice.
+        """
+        Write cosmology output parameters for a cosmology splice.
         """
 
         mylog.info("Writing redshift output list to %s.", filename)

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/fits/data_structures.py
--- a/yt/frontends/fits/data_structures.py
+++ b/yt/frontends/fits/data_structures.py
@@ -165,7 +165,7 @@
                     units = self._determine_image_units(hdu.header, known_units)
                     try:
                         # Grab field name from btype
-                        fname = hdu.header["btype"].lower()
+                        fname = hdu.header["btype"]
                     except KeyError:
                         # Try to guess the name from the units
                         fname = self._guess_name_from_units(units)
@@ -205,18 +205,6 @@
                                   "the same dimensions as the primary and will not be " +
                                   "available as a field.")
 
-        # For line fields, we still read the primary field. Not sure how to extend this
-        # For now, we pick off the first field from the field list.
-        line_db = self.dataset.line_database
-        primary_fname = self.field_list[0][1]
-        for k, v in iteritems(line_db):
-            mylog.info("Adding line field: %s at frequency %g GHz" % (k, v))
-            self.field_list.append((self.dataset_type, k))
-            self._ext_map[k] = self._ext_map[primary_fname]
-            self._axis_map[k] = self._axis_map[primary_fname]
-            self._file_map[k] = self._file_map[primary_fname]
-            self.dataset.field_units[k] = self.dataset.field_units[primary_fname]
-
     def _count_grids(self):
         self.num_grids = self.ds.parameters["nprocs"]
 
@@ -242,19 +230,11 @@
                 bbox = np.array([[le,re] for le, re in zip(ds.domain_left_edge,
                                                            ds.domain_right_edge)])
                 dims = np.array(ds.domain_dimensions)
-                # If we are creating a dataset of lines, only decompose along the position axes
-                if len(ds.line_database) > 0:
-                    dims[ds.spec_axis] = 1
                 psize = get_psize(dims, self.num_grids)
                 gle, gre, shapes, slices = decompose_array(dims, psize, bbox)
                 self.grid_left_edge = self.ds.arr(gle, "code_length")
                 self.grid_right_edge = self.ds.arr(gre, "code_length")
                 self.grid_dimensions = np.array([shape for shape in shapes], dtype="int32")
-                # If we are creating a dataset of lines, only decompose along the position axes
-                if len(ds.line_database) > 0:
-                    self.grid_left_edge[:,ds.spec_axis] = ds.domain_left_edge[ds.spec_axis]
-                    self.grid_right_edge[:,ds.spec_axis] = ds.domain_right_edge[ds.spec_axis]
-                    self.grid_dimensions[:,ds.spec_axis] = ds.domain_dimensions[ds.spec_axis]
         else:
             self.grid_left_edge[0,:] = ds.domain_left_edge
             self.grid_right_edge[0,:] = ds.domain_right_edge
@@ -322,8 +302,6 @@
                  nan_mask=None,
                  spectral_factor=1.0,
                  z_axis_decomp=False,
-                 line_database=None,
-                 line_width=None,
                  suppress_astropy_warnings=True,
                  parameters=None,
                  units_override=None):
@@ -336,19 +314,6 @@
         self.z_axis_decomp = z_axis_decomp
         self.spectral_factor = spectral_factor
 
-        if line_width is not None:
-            self.line_width = YTQuantity(line_width[0], line_width[1])
-            self.line_units = line_width[1]
-            mylog.info("For line folding, spectral_factor = 1.0")
-            self.spectral_factor = 1.0
-        else:
-            self.line_width = None
-
-        self.line_database = {}
-        if line_database is not None:
-            for k in line_database:
-                self.line_database[k] = YTQuantity(line_database[k], self.line_units)
-
         if suppress_astropy_warnings:
             warnings.filterwarnings('ignore', module="astropy", append=True)
         auxiliary_files = ensure_list(auxiliary_files)
@@ -361,13 +326,13 @@
             self.nan_mask = {"all":nan_mask}
         elif isinstance(nan_mask, dict):
             self.nan_mask = nan_mask
-        if isinstance(self.filenames[0], _astropy.pyfits.hdu.image._ImageBaseHDU):
-            self._handle = FITSFileHandler(self.filenames[0])
-            fn = "InMemoryFITSImage_%s" % (uuid.uuid4().hex)
+        self._handle = FITSFileHandler(self.filenames[0])
+        if (isinstance(self.filenames[0], _astropy.pyfits.hdu.image._ImageBaseHDU) or
+            isinstance(self.filenames[0], _astropy.pyfits.HDUList)):
+            fn = "InMemoryFITSFile_%s" % uuid.uuid4().hex
         else:
-            self._handle = FITSFileHandler(self.filenames[0])
             fn = self.filenames[0]
-        self._handle._fits_files = [self._handle]
+        self._handle._fits_files.append(self._handle)
         if self.num_files > 1:
             for fits_file in auxiliary_files:
                 if isinstance(fits_file, _astropy.pyfits.hdu.image._ImageBaseHDU):
@@ -540,20 +505,14 @@
 
         # If nprocs is None, do some automatic decomposition of the domain
         if self.specified_parameters["nprocs"] is None:
-            if len(self.line_database) > 0:
-                dims = 2
-            else:
-                dims = self.dimensionality
             if self.z_axis_decomp:
                 nprocs = np.around(self.domain_dimensions[2]/8).astype("int")
             else:
-                nprocs = np.around(np.prod(self.domain_dimensions)/32**dims).astype("int")
+                nprocs = np.around(np.prod(self.domain_dimensions)/32**self.dimensionality).astype("int")
             self.parameters["nprocs"] = max(min(nprocs, 512), 1)
         else:
             self.parameters["nprocs"] = self.specified_parameters["nprocs"]
 
-        self.reversed = False
-
         # Check to see if this data is in some kind of (Lat,Lon,Vel) format
         self.spec_cube = False
         x = 0
@@ -618,41 +577,23 @@
             self._z0 = self.wcs.wcs.crval[self.spec_axis]
             self.spec_unit = str(self.wcs.wcs.cunit[self.spec_axis])
 
-            if self.line_width is not None:
-                if self._dz < 0.0:
-                    self.reversed = True
-                    le = self.dims[self.spec_axis]+0.5
-                else:
-                    le = 0.5
-                self.line_width = self.line_width.in_units(self.spec_unit)
-                self.freq_begin = (le-self._p0)*self._dz + self._z0
-                # We now reset these so that they are consistent
-                # with the new setup
-                self._dz = np.abs(self._dz)
-                self._p0 = 0.0
-                self._z0 = 0.0
-                nz = np.rint(self.line_width.value/self._dz).astype("int")
-                self.line_width = self._dz*nz
-                self.domain_left_edge[self.spec_axis] = -0.5*float(nz)
-                self.domain_right_edge[self.spec_axis] = 0.5*float(nz)
-                self.domain_dimensions[self.spec_axis] = nz
-            else:
-                if self.spectral_factor == "auto":
-                    self.spectral_factor = float(max(self.domain_dimensions[[self.lon_axis,
-                                                                             self.lat_axis]]))
-                    self.spectral_factor /= self.domain_dimensions[self.spec_axis]
-                    mylog.info("Setting the spectral factor to %f" % (self.spectral_factor))
-                Dz = self.domain_right_edge[self.spec_axis]-self.domain_left_edge[self.spec_axis]
-                self.domain_right_edge[self.spec_axis] = self.domain_left_edge[self.spec_axis] + \
-                                                        self.spectral_factor*Dz
-                self._dz /= self.spectral_factor
-                self._p0 = (self._p0-0.5)*self.spectral_factor + 0.5
+            if self.spectral_factor == "auto":
+                self.spectral_factor = float(max(self.domain_dimensions[[self.lon_axis,
+                                                                         self.lat_axis]]))
+                self.spectral_factor /= self.domain_dimensions[self.spec_axis]
+                mylog.info("Setting the spectral factor to %f" % (self.spectral_factor))
+            Dz = self.domain_right_edge[self.spec_axis]-self.domain_left_edge[self.spec_axis]
+            self.domain_right_edge[self.spec_axis] = self.domain_left_edge[self.spec_axis] + \
+                                                     self.spectral_factor*Dz
+            self._dz /= self.spectral_factor
+            self._p0 = (self._p0-0.5)*self.spectral_factor + 0.5
+            
         else:
 
             self.wcs_2d = self.wcs
             self.spec_axis = 2
             self.spec_name = "z"
-            self.spec_unit = "code length"
+            self.spec_unit = "code_length"
 
     def spec2pixel(self, spec_value):
         sv = self.arr(spec_value).in_units(self.spec_unit)

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/fits/io.py
--- a/yt/frontends/fits/io.py
+++ b/yt/frontends/fits/io.py
@@ -24,12 +24,6 @@
         super(IOHandlerFITS, self).__init__(ds)
         self.ds = ds
         self._handle = ds._handle
-        if self.ds.line_width is not None:
-            self.line_db = self.ds.line_database
-            self.dz = self.ds.line_width/self.domain_dimensions[self.ds.spec_axis]
-        else:
-            self.line_db = None
-            self.dz = 1.
 
     def _read_particles(self, fields_to_read, type, args, grid_list,
             count_list, conv_factors):
@@ -79,32 +73,15 @@
         dx = self.ds.domain_width/self.ds.domain_dimensions
         for field in fields:
             ftype, fname = field
-            tmp_fname = fname
-            if fname in self.ds.line_database:
-                fname = self.ds.field_list[0][1]
             f = self.ds.index._file_map[fname]
             ds = f[self.ds.index._ext_map[fname]]
             bzero, bscale = self.ds.index._scale_map[fname]
-            fname = tmp_fname
             ind = 0
             for chunk in chunks:
                 for g in chunk.objs:
                     start = ((g.LeftEdge-self.ds.domain_left_edge)/dx).to_ndarray().astype("int")
                     end = start + g.ActiveDimensions
-                    if self.line_db is not None and fname in self.line_db:
-                        my_off = self.line_db.get(fname).in_units(self.ds.spec_unit).value
-                        my_off = my_off - 0.5*self.ds.line_width
-                        my_off = int((my_off-self.ds.freq_begin)/self.dz)
-                        my_off = max(my_off, 0)
-                        my_off = min(my_off, self.ds.dims[self.ds.spec_axis]-1)
-                        start[self.ds.spec_axis] += my_off
-                        end[self.ds.spec_axis] += my_off
-                        mylog.debug("Reading from " + str(start) + str(end))
                     slices = [slice(start[i],end[i]) for i in range(3)]
-                    if self.ds.reversed:
-                        new_start = self.ds.dims[self.ds.spec_axis]-1-start[self.ds.spec_axis]
-                        new_end = max(self.ds.dims[self.ds.spec_axis]-1-end[self.ds.spec_axis],0)
-                        slices[self.ds.spec_axis] = slice(new_start,new_end,-1)
                     if self.ds.dimensionality == 2:
                         nx, ny = g.ActiveDimensions[:2]
                         nz = 1
@@ -115,13 +92,6 @@
                         data = ds.data[idx,slices[2],slices[1],slices[0]].transpose()
                     else:
                         data = ds.data[slices[2],slices[1],slices[0]].transpose()
-                    if self.line_db is not None:
-                        nz1 = data.shape[self.ds.spec_axis]
-                        nz2 = g.ActiveDimensions[self.ds.spec_axis]
-                        if nz1 != nz2:
-                            old_data = data.copy()
-                            data = np.zeros(g.ActiveDimensions)
-                            data[:,:,nz2-nz1:] = old_data
                     if fname in self.ds.nan_mask:
                         data[np.isnan(data)] = self.ds.nan_mask[fname]
                     elif "all" in self.ds.nan_mask:

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/fits/misc.py
--- a/yt/frontends/fits/misc.py
+++ b/yt/frontends/fits/misc.py
@@ -17,6 +17,8 @@
 from yt.utilities.on_demand_imports import _astropy
 from yt.funcs import mylog, get_image_suffix
 from yt.visualization._mpl_imports import FigureCanvasAgg
+from yt.units.yt_array import YTQuantity, YTArray
+from yt.utilities.fits_image import FITSImageBuffer
 
 import os
 
@@ -68,6 +70,70 @@
                      validators = [ValidateSpatial()],
                      display_name="Counts (%s-%s keV)" % (emin, emax))
 
+def create_spectral_slabs(filename, slab_centers, slab_width,
+                          **kwargs):
+    r"""
+    Given a dictionary of spectral slab centers and a width in
+    spectral units, extract data from a spectral cube at these slab
+    centers and return a `FITSDataset` instance containing the different 
+    slabs as separate yt fields. Useful for extracting individual 
+    lines from a spectral cube and separating them out as different fields. 
+
+    Requires the SpectralCube (http://spectral-cube.readthedocs.org)
+    library.
+
+    All keyword arguments will be passed on to the `FITSDataset` constructor.
+
+    Parameters
+    ----------
+    filename : string
+        The spectral cube FITS file to extract the data from.
+    slab_centers : dict of (float, string) tuples or YTQuantities
+        The centers of the slabs, where the keys are the names
+        of the new fields and the values are (float, string) tuples or
+        YTQuantities, specifying a value for each center and its unit.
+    slab_width : YTQuantity or (float, string) tuple
+        The width of the slab along the spectral axis.
+
+    Examples
+    --------
+    >>> slab_centers = {'13CN': (218.03117, 'GHz'),
+    ...                 'CH3CH2CHO': (218.284256, 'GHz'),
+    ...                 'CH3NH2': (218.40956, 'GHz')}
+    >>> slab_width = (0.05, "GHz")
+    >>> ds = create_spectral_slabs("intensity_cube.fits", 
+    ...                            slab_centers, slab_width,
+    ...                            nan_mask=0.0)
+    """
+    from spectral_cube import SpectralCube
+    from yt.frontends.fits.api import FITSDataset
+    cube = SpectralCube.read(filename)
+    if not isinstance(slab_width, YTQuantity):
+        slab_width = YTQuantity(slab_width[0], slab_width[1])
+    slab_data = {}
+    field_units = cube.header.get("bunit", "dimensionless")
+    for k, v in slab_centers.items():
+        if not isinstance(v, YTQuantity):
+            slab_center = YTQuantity(v[0], v[1])
+        else:
+            slab_center = v
+        mylog.info("Adding slab field %s at %g %s" %
+                   (k, slab_center.v, slab_center.units))
+        slab_lo = (slab_center-0.5*slab_width).to_astropy()
+        slab_hi = (slab_center+0.5*slab_width).to_astropy()
+        subcube = cube.spectral_slab(slab_lo, slab_hi)
+        slab_data[k] = YTArray(subcube.filled_data[:,:,:], field_units)
+    width = subcube.header["naxis3"]*cube.header["cdelt3"]
+    w = subcube.wcs.copy()
+    w.wcs.crpix[-1] = 0.5
+    w.wcs.crval[-1] = -0.5*width
+    fid = FITSImageBuffer(slab_data, wcs=w)
+    for hdu in fid:
+        hdu.header.pop("RESTFREQ", None)
+        hdu.header.pop("RESTFRQ", None)
+    ds = FITSDataset(fid, **kwargs)
+    return ds
+
 def ds9_region(ds, reg, obj=None, field_parameters=None):
     r"""
     Create a data container from a ds9 region file. Requires the pyregion

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/gadget/api.py
--- a/yt/frontends/gadget/api.py
+++ b/yt/frontends/gadget/api.py
@@ -7,7 +7,7 @@
 """
 
 #-----------------------------------------------------------------------------
-# Copyright (c) 2014, yt Development Team.
+# Copyright (c) 2014-2015, yt Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
@@ -23,4 +23,7 @@
     IOHandlerGadgetBinary, \
     IOHandlerGadgetHDF5
 
+from .simulation_handling import \
+    GadgetSimulation
+
 from . import tests

diff -r 696a6134f3f070d4b55fcfc4c2554db563aab11e -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 yt/frontends/gadget/data_structures.py
--- a/yt/frontends/gadget/data_structures.py
+++ b/yt/frontends/gadget/data_structures.py
@@ -18,6 +18,7 @@
 import h5py
 import numpy as np
 import stat
+import struct
 import os
 import types
 
@@ -242,10 +243,59 @@
         self.mass_unit = self.quan(mass_unit[0], mass_unit[1])
         self.time_unit = self.length_unit / self.velocity_unit
 
+    @staticmethod
+    def _validate_header(filename):
+        '''
+        This method automatically detects whether the Gadget file is big/little endian 
+        and is not corrupt/invalid using the first 4 bytes in the file.  It returns a 
+        tuple of (Valid, endianswap) where Valid is a boolean that is true if the file 
+        is a Gadget binary file, and endianswap is the endianness character '>' or '<'. 
+        '''
+        try:
+            f = open(filename,'rb')
+        except IOError:
+            try:
+                f = open(filename+".0")
+            except IOError:
+                return False, 1
+        
+        # First int32 is 256 for a Gadget2 binary file with SnapFormat=1,
+        # 8 for a Gadget2 binary file with SnapFormat=2 file, 
+        # or the byte swapped equivalents (65536 and 134217728).
+        # The int32 following the header (first 4+256 bytes) must equal this
+        # number.
+        (rhead,) = struct.unpack('<I',f.read(4))
+        # Use value to check endianess
+        if rhead == 256:
+            endianswap = '<'
+        elif rhead == 65536:
+            endianswap = '>'
+        # Disabled for now (does any one still use SnapFormat=2?)
+        # If so, alternate read would be needed based on header.
+        # elif rhead == 8:
+        #     return True, '<'
+        # elif rhead == 134217728:
+        #     return True, '>'
+        else:
+            f.close()
+            return False, 1
+        # Read in particle number from header
+        np0 = sum(struct.unpack(endianswap+'IIIIII',f.read(6*4)))
+        # Read in size of position block. It should be 4 bytes per float, 
+        # with 3 coordinates (x,y,z) per particle. (12 bytes per particle)
+        f.seek(4+256+4,0)
+        np1 = struct.unpack(endianswap+'I',f.read(4))[0]/(4*3)
+        f.close()
+        # Compare
+        if np0 == np1:
+            return True, endianswap
+        else:
+            return False, 1
+
     @classmethod
     def _is_valid(self, *args, **kwargs):
-        # We do not allow load() of these files.
-        return False
+        # First 4 bytes used to check load
+        return GadgetDataset._validate_header(args[0])[0]
 
 class GadgetHDF5Dataset(GadgetDataset):
     _file_class = ParticleFile

This diff is so big that we needed to truncate the remainder.

https://bitbucket.org/yt_analysis/yt/commits/45467416f055/
Changeset:   45467416f055
Branch:      yt
User:        jzuhone
Date:        2015-06-02 00:36:26+00:00
Summary:     Merge
Affected #:  16 files

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe distribute_setup.py
--- a/distribute_setup.py
+++ /dev/null
@@ -1,541 +0,0 @@
-#!python
-"""Bootstrap distribute installation
-
-If you want to use setuptools in your package's setup.py, just include this
-file in the same directory with it, and add this to the top of your setup.py::
-
-    from distribute_setup import use_setuptools
-    use_setuptools()
-
-If you want to require a specific version of setuptools, set a download
-mirror, or use an alternate download directory, you can do so by supplying
-the appropriate options to ``use_setuptools()``.
-
-This file can also be run as a script to install or upgrade setuptools.
-"""
-import os
-import shutil
-import sys
-import time
-import fnmatch
-import tempfile
-import tarfile
-import optparse
-
-from distutils import log
-
-try:
-    from site import USER_SITE
-except ImportError:
-    USER_SITE = None
-
-try:
-    import subprocess
-
-    def _python_cmd(*args):
-        args = (sys.executable,) + args
-        return subprocess.call(args) == 0
-
-except ImportError:
-    # will be used for python 2.3
-    def _python_cmd(*args):
-        args = (sys.executable,) + args
-        # quoting arguments if windows
-        if sys.platform == 'win32':
-            def quote(arg):
-                if ' ' in arg:
-                    return '"%s"' % arg
-                return arg
-            args = [quote(arg) for arg in args]
-        return os.spawnl(os.P_WAIT, sys.executable, *args) == 0
-
-DEFAULT_VERSION = "0.6.32"
-DEFAULT_URL = "http://pypi.python.org/packages/source/d/distribute/"
-SETUPTOOLS_FAKED_VERSION = "0.6c11"
-
-SETUPTOOLS_PKG_INFO = """\
-Metadata-Version: 1.0
-Name: setuptools
-Version: %s
-Summary: xxxx
-Home-page: xxx
-Author: xxx
-Author-email: xxx
-License: xxx
-Description: xxx
-""" % SETUPTOOLS_FAKED_VERSION
-
-
-def _install(tarball, install_args=()):
-    # extracting the tarball
-    tmpdir = tempfile.mkdtemp()
-    log.warn('Extracting in %s', tmpdir)
-    old_wd = os.getcwd()
-    try:
-        os.chdir(tmpdir)
-        tar = tarfile.open(tarball)
-        _extractall(tar)
-        tar.close()
-
-        # going in the directory
-        subdir = os.path.join(tmpdir, os.listdir(tmpdir)[0])
-        os.chdir(subdir)
-        log.warn('Now working in %s', subdir)
-
-        # installing
-        log.warn('Installing Distribute')
-        if not _python_cmd('setup.py', 'install', *install_args):
-            log.warn('Something went wrong during the installation.')
-            log.warn('See the error message above.')
-            # exitcode will be 2
-            return 2
-    finally:
-        os.chdir(old_wd)
-        shutil.rmtree(tmpdir)
-
-
-def _build_egg(egg, tarball, to_dir):
-    # extracting the tarball
-    tmpdir = tempfile.mkdtemp()
-    log.warn('Extracting in %s', tmpdir)
-    old_wd = os.getcwd()
-    try:
-        os.chdir(tmpdir)
-        tar = tarfile.open(tarball)
-        _extractall(tar)
-        tar.close()
-
-        # going in the directory
-        subdir = os.path.join(tmpdir, os.listdir(tmpdir)[0])
-        os.chdir(subdir)
-        log.warn('Now working in %s', subdir)
-
-        # building an egg
-        log.warn('Building a Distribute egg in %s', to_dir)
-        _python_cmd('setup.py', '-q', 'bdist_egg', '--dist-dir', to_dir)
-
-    finally:
-        os.chdir(old_wd)
-        shutil.rmtree(tmpdir)
-    # returning the result
-    log.warn(egg)
-    if not os.path.exists(egg):
-        raise IOError('Could not build the egg.')
-
-
-def _do_download(version, download_base, to_dir, download_delay):
-    egg = os.path.join(to_dir, 'distribute-%s-py%d.%d.egg'
-                       % (version, sys.version_info[0], sys.version_info[1]))
-    if not os.path.exists(egg):
-        tarball = download_setuptools(version, download_base,
-                                      to_dir, download_delay)
-        _build_egg(egg, tarball, to_dir)
-    sys.path.insert(0, egg)
-    import setuptools
-    setuptools.bootstrap_install_from = egg
-
-
-def use_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
-                   to_dir=os.curdir, download_delay=15, no_fake=True):
-    # making sure we use the absolute path
-    to_dir = os.path.abspath(to_dir)
-    was_imported = 'pkg_resources' in sys.modules or \
-        'setuptools' in sys.modules
-    try:
-        try:
-            import pkg_resources
-            if not hasattr(pkg_resources, '_distribute'):
-                if not no_fake:
-                    _fake_setuptools()
-                raise ImportError
-        except ImportError:
-            return _do_download(version, download_base, to_dir, download_delay)
-        try:
-            pkg_resources.require("distribute>=" + version)
-            return
-        except pkg_resources.VersionConflict:
-            e = sys.exc_info()[1]
-            if was_imported:
-                sys.stderr.write(
-                "The required version of distribute (>=%s) is not available,\n"
-                "and can't be installed while this script is running. Please\n"
-                "install a more recent version first, using\n"
-                "'easy_install -U distribute'."
-                "\n\n(Currently using %r)\n" % (version, e.args[0]))
-                sys.exit(2)
-            else:
-                del pkg_resources, sys.modules['pkg_resources']    # reload ok
-                return _do_download(version, download_base, to_dir,
-                                    download_delay)
-        except pkg_resources.DistributionNotFound:
-            return _do_download(version, download_base, to_dir,
-                                download_delay)
-    finally:
-        if not no_fake:
-            _create_fake_setuptools_pkg_info(to_dir)
-
-
-def download_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
-                        to_dir=os.curdir, delay=15):
-    """Download distribute from a specified location and return its filename
-
-    `version` should be a valid distribute version number that is available
-    as an egg for download under the `download_base` URL (which should end
-    with a '/'). `to_dir` is the directory where the egg will be downloaded.
-    `delay` is the number of seconds to pause before an actual download
-    attempt.
-    """
-    # making sure we use the absolute path
-    to_dir = os.path.abspath(to_dir)
-    try:
-        from urllib.request import urlopen
-    except ImportError:
-        from urllib2 import urlopen
-    tgz_name = "distribute-%s.tar.gz" % version
-    url = download_base + tgz_name
-    saveto = os.path.join(to_dir, tgz_name)
-    src = dst = None
-    if not os.path.exists(saveto):  # Avoid repeated downloads
-        try:
-            log.warn("Downloading %s", url)
-            src = urlopen(url)
-            # Read/write all in one block, so we don't create a corrupt file
-            # if the download is interrupted.
-            data = src.read()
-            dst = open(saveto, "wb")
-            dst.write(data)
-        finally:
-            if src:
-                src.close()
-            if dst:
-                dst.close()
-    return os.path.realpath(saveto)
-
-
-def _no_sandbox(function):
-    def __no_sandbox(*args, **kw):
-        try:
-            from setuptools.sandbox import DirectorySandbox
-            if not hasattr(DirectorySandbox, '_old'):
-                def violation(*args):
-                    pass
-                DirectorySandbox._old = DirectorySandbox._violation
-                DirectorySandbox._violation = violation
-                patched = True
-            else:
-                patched = False
-        except ImportError:
-            patched = False
-
-        try:
-            return function(*args, **kw)
-        finally:
-            if patched:
-                DirectorySandbox._violation = DirectorySandbox._old
-                del DirectorySandbox._old
-
-    return __no_sandbox
-
-
-def _patch_file(path, content):
-    """Will backup the file then patch it"""
-    existing_content = open(path).read()
-    if existing_content == content:
-        # already patched
-        log.warn('Already patched.')
-        return False
-    log.warn('Patching...')
-    _rename_path(path)
-    f = open(path, 'w')
-    try:
-        f.write(content)
-    finally:
-        f.close()
-    return True
-
-_patch_file = _no_sandbox(_patch_file)
-
-
-def _same_content(path, content):
-    return open(path).read() == content
-
-
-def _rename_path(path):
-    new_name = path + '.OLD.%s' % time.time()
-    log.warn('Renaming %s to %s', path, new_name)
-    os.rename(path, new_name)
-    return new_name
-
-
-def _remove_flat_installation(placeholder):
-    if not os.path.isdir(placeholder):
-        log.warn('Unknown installation at %s', placeholder)
-        return False
-    found = False
-    for file in os.listdir(placeholder):
-        if fnmatch.fnmatch(file, 'setuptools*.egg-info'):
-            found = True
-            break
-    if not found:
-        log.warn('Could not locate setuptools*.egg-info')
-        return
-
-    log.warn('Moving elements out of the way...')
-    pkg_info = os.path.join(placeholder, file)
-    if os.path.isdir(pkg_info):
-        patched = _patch_egg_dir(pkg_info)
-    else:
-        patched = _patch_file(pkg_info, SETUPTOOLS_PKG_INFO)
-
-    if not patched:
-        log.warn('%s already patched.', pkg_info)
-        return False
-    # now let's move the files out of the way
-    for element in ('setuptools', 'pkg_resources.py', 'site.py'):
-        element = os.path.join(placeholder, element)
-        if os.path.exists(element):
-            _rename_path(element)
-        else:
-            log.warn('Could not find the %s element of the '
-                     'Setuptools distribution', element)
-    return True
-
-_remove_flat_installation = _no_sandbox(_remove_flat_installation)
-
-
-def _after_install(dist):
-    log.warn('After install bootstrap.')
-    placeholder = dist.get_command_obj('install').install_purelib
-    _create_fake_setuptools_pkg_info(placeholder)
-
-
-def _create_fake_setuptools_pkg_info(placeholder):
-    if not placeholder or not os.path.exists(placeholder):
-        log.warn('Could not find the install location')
-        return
-    pyver = '%s.%s' % (sys.version_info[0], sys.version_info[1])
-    setuptools_file = 'setuptools-%s-py%s.egg-info' % \
-            (SETUPTOOLS_FAKED_VERSION, pyver)
-    pkg_info = os.path.join(placeholder, setuptools_file)
-    if os.path.exists(pkg_info):
-        log.warn('%s already exists', pkg_info)
-        return
-
-    log.warn('Creating %s', pkg_info)
-    try:
-        f = open(pkg_info, 'w')
-    except EnvironmentError:
-        log.warn("Don't have permissions to write %s, skipping", pkg_info)
-        return
-    try:
-        f.write(SETUPTOOLS_PKG_INFO)
-    finally:
-        f.close()
-
-    pth_file = os.path.join(placeholder, 'setuptools.pth')
-    log.warn('Creating %s', pth_file)
-    f = open(pth_file, 'w')
-    try:
-        f.write(os.path.join(os.curdir, setuptools_file))
-    finally:
-        f.close()
-
-_create_fake_setuptools_pkg_info = _no_sandbox(
-    _create_fake_setuptools_pkg_info
-)
-
-
-def _patch_egg_dir(path):
-    # let's check if it's already patched
-    pkg_info = os.path.join(path, 'EGG-INFO', 'PKG-INFO')
-    if os.path.exists(pkg_info):
-        if _same_content(pkg_info, SETUPTOOLS_PKG_INFO):
-            log.warn('%s already patched.', pkg_info)
-            return False
-    _rename_path(path)
-    os.mkdir(path)
-    os.mkdir(os.path.join(path, 'EGG-INFO'))
-    pkg_info = os.path.join(path, 'EGG-INFO', 'PKG-INFO')
-    f = open(pkg_info, 'w')
-    try:
-        f.write(SETUPTOOLS_PKG_INFO)
-    finally:
-        f.close()
-    return True
-
-_patch_egg_dir = _no_sandbox(_patch_egg_dir)
-
-
-def _before_install():
-    log.warn('Before install bootstrap.')
-    _fake_setuptools()
-
-
-def _under_prefix(location):
-    if 'install' not in sys.argv:
-        return True
-    args = sys.argv[sys.argv.index('install') + 1:]
-    for index, arg in enumerate(args):
-        for option in ('--root', '--prefix'):
-            if arg.startswith('%s=' % option):
-                top_dir = arg.split('root=')[-1]
-                return location.startswith(top_dir)
-            elif arg == option:
-                if len(args) > index:
-                    top_dir = args[index + 1]
-                    return location.startswith(top_dir)
-        if arg == '--user' and USER_SITE is not None:
-            return location.startswith(USER_SITE)
-    return True
-
-
-def _fake_setuptools():
-    log.warn('Scanning installed packages')
-    try:
-        import pkg_resources
-    except ImportError:
-        # we're cool
-        log.warn('Setuptools or Distribute does not seem to be installed.')
-        return
-    ws = pkg_resources.working_set
-    try:
-        setuptools_dist = ws.find(
-            pkg_resources.Requirement.parse('setuptools', replacement=False)
-            )
-    except TypeError:
-        # old distribute API
-        setuptools_dist = ws.find(
-            pkg_resources.Requirement.parse('setuptools')
-        )
-
-    if setuptools_dist is None:
-        log.warn('No setuptools distribution found')
-        return
-    # detecting if it was already faked
-    setuptools_location = setuptools_dist.location
-    log.warn('Setuptools installation detected at %s', setuptools_location)
-
-    # if --root or --preix was provided, and if
-    # setuptools is not located in them, we don't patch it
-    if not _under_prefix(setuptools_location):
-        log.warn('Not patching, --root or --prefix is installing Distribute'
-                 ' in another location')
-        return
-
-    # let's see if its an egg
-    if not setuptools_location.endswith('.egg'):
-        log.warn('Non-egg installation')
-        res = _remove_flat_installation(setuptools_location)
-        if not res:
-            return
-    else:
-        log.warn('Egg installation')
-        pkg_info = os.path.join(setuptools_location, 'EGG-INFO', 'PKG-INFO')
-        if (os.path.exists(pkg_info) and
-            _same_content(pkg_info, SETUPTOOLS_PKG_INFO)):
-            log.warn('Already patched.')
-            return
-        log.warn('Patching...')
-        # let's create a fake egg replacing setuptools one
-        res = _patch_egg_dir(setuptools_location)
-        if not res:
-            return
-    log.warn('Patching complete.')
-    _relaunch()
-
-
-def _relaunch():
-    log.warn('Relaunching...')
-    # we have to relaunch the process
-    # pip marker to avoid a relaunch bug
-    _cmd1 = ['-c', 'install', '--single-version-externally-managed']
-    _cmd2 = ['-c', 'install', '--record']
-    if sys.argv[:3] == _cmd1 or sys.argv[:3] == _cmd2:
-        sys.argv[0] = 'setup.py'
-    args = [sys.executable] + sys.argv
-    sys.exit(subprocess.call(args))
-
-
-def _extractall(self, path=".", members=None):
-    """Extract all members from the archive to the current working
-       directory and set owner, modification time and permissions on
-       directories afterwards. `path' specifies a different directory
-       to extract to. `members' is optional and must be a subset of the
-       list returned by getmembers().
-    """
-    import copy
-    import operator
-    from tarfile import ExtractError
-    directories = []
-
-    if members is None:
-        members = self
-
-    for tarinfo in members:
-        if tarinfo.isdir():
-            # Extract directories with a safe mode.
-            directories.append(tarinfo)
-            tarinfo = copy.copy(tarinfo)
-            tarinfo.mode = 448  # decimal for oct 0700
-        self.extract(tarinfo, path)
-
-    # Reverse sort directories.
-    if sys.version_info < (2, 4):
-        def sorter(dir1, dir2):
-            return cmp(dir1.name, dir2.name)
-        directories.sort(sorter)
-        directories.reverse()
-    else:
-        directories.sort(key=operator.attrgetter('name'), reverse=True)
-
-    # Set correct owner, mtime and filemode on directories.
-    for tarinfo in directories:
-        dirpath = os.path.join(path, tarinfo.name)
-        try:
-            self.chown(tarinfo, dirpath)
-            self.utime(tarinfo, dirpath)
-            self.chmod(tarinfo, dirpath)
-        except ExtractError:
-            e = sys.exc_info()[1]
-            if self.errorlevel > 1:
-                raise
-            else:
-                self._dbg(1, "tarfile: %s" % e)
-
-
-def _build_install_args(options):
-    """
-    Build the arguments to 'python setup.py install' on the distribute package
-    """
-    install_args = []
-    if options.user_install:
-        if sys.version_info < (2, 6):
-            log.warn("--user requires Python 2.6 or later")
-            raise SystemExit(1)
-        install_args.append('--user')
-    return install_args
-
-def _parse_args():
-    """
-    Parse the command line for options
-    """
-    parser = optparse.OptionParser()
-    parser.add_option(
-        '--user', dest='user_install', action='store_true', default=False,
-        help='install in user site package (requires Python 2.6 or later)')
-    parser.add_option(
-        '--download-base', dest='download_base', metavar="URL",
-        default=DEFAULT_URL,
-        help='alternative URL from where to download the distribute package')
-    options, args = parser.parse_args()
-    # positional arguments are ignored
-    return options
-
-def main(version=DEFAULT_VERSION):
-    """Install or upgrade setuptools and EasyInstall"""
-    options = _parse_args()
-    tarball = download_setuptools(download_base=options.download_base)
-    return _install(tarball, _build_install_args(options))
-
-if __name__ == '__main__':
-    sys.exit(main())

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe doc/install_script.sh
--- a/doc/install_script.sh
+++ b/doc/install_script.sh
@@ -1,18 +1,14 @@
 #
 # Hi there!  Welcome to the yt installation script.
 #
+# First things first, if you experience problems, please visit the Help 
+# section at http://yt-project.org.
+#
 # This script is designed to create a fully isolated Python installation
 # with the dependencies you need to run yt.
 #
-# There are a few options, but you only need to set *one* of them.  And
-# that's the next one, DEST_DIR.  But, if you want to use an existing HDF5
-# installation you can set HDF5_DIR, or if you want to use some other
-# subversion checkout of yt, you can set YT_DIR, too.  (It'll already
-# check the current directory and one up.
-#
-# If you experience problems, please visit the Help section at 
-# http://yt-project.org.
-#
+# There are a few options, but you only need to set *one* of them, which is 
+# the next one, DEST_DIR:
 
 DEST_SUFFIX="yt-`uname -m`"
 DEST_DIR="`pwd`/${DEST_SUFFIX/ /}"   # Installation location
@@ -23,16 +19,25 @@
     DEST_DIR=${YT_DEST}
 fi
 
+# What follows are some other options that you may or may not need to change.
+
 # Here's where you put the HDF5 path if you like; otherwise it'll download it
 # and install it on its own
 #HDF5_DIR=
 
+# If you've got yt some other place, set this to point to it. The script will
+# already check the current directory and the one above it in the tree.
+YT_DIR=""
+
 # If you need to supply arguments to the NumPy or SciPy build, supply them here
 # This one turns on gfortran manually:
 #NUMPY_ARGS="--fcompiler=gnu95"
 # If you absolutely can't get the fortran to work, try this:
 #NUMPY_ARGS="--fcompiler=fake"
 
+INST_PY3=0      # Install Python 3 along with Python 2. If this is turned
+                # on, all Python packages (including yt) will be installed
+                # in Python 3 (except Mercurial, which requires Python 2).
 INST_HG=1       # Install Mercurial or not?  If hg is not already
                 # installed, yt cannot be installed.
 INST_ZLIB=1     # On some systems (Kraken) matplotlib has issues with
@@ -50,9 +55,6 @@
 INST_ROCKSTAR=0 # Install the Rockstar halo finder?
 INST_SCIPY=0    # Install scipy?
 
-# If you've got yt some other place, set this to point to it.
-YT_DIR=""
-
 # If you need to pass anything to matplotlib, do so here.
 MPL_SUPP_LDFLAGS=""
 MPL_SUPP_CFLAGS=""
@@ -111,6 +113,7 @@
     echo INST_SQLITE3=${INST_SQLITE3} >> ${CONFIG_FILE}
     echo INST_PYX=${INST_PYX} >> ${CONFIG_FILE}
     echo INST_0MQ=${INST_0MQ} >> ${CONFIG_FILE}
+    echo INST_PY3=${INST_PY3} >> ${CONFIG_FILE}
     echo INST_ROCKSTAR=${INST_ROCKSTAR} >> ${CONFIG_FILE}
     echo INST_SCIPY=${INST_SCIPY} >> ${CONFIG_FILE}
     echo YT_DIR=${YT_DIR} >> ${CONFIG_FILE}
@@ -415,6 +418,10 @@
 get_willwont ${INST_SQLITE3}
 echo "be installing SQLite3"
 
+printf "%-15s = %s so I " "INST_PY3" "${INST_PY3}"
+get_willwont ${INST_PY3}
+echo "be installing Python 3"
+
 printf "%-15s = %s so I " "INST_HG" "${INST_HG}"
 get_willwont ${INST_HG}
 echo "be installing Mercurial"
@@ -487,6 +494,13 @@
     exit 1
 }
 
+if [ $INST_PY3 -eq 1 ]
+then
+	 PYTHON_EXEC='python3.4'
+else 
+	 PYTHON_EXEC='python2.7'
+fi
+
 function do_setup_py
 {
     [ -e $1/done ] && return
@@ -501,21 +515,27 @@
     [ ! -e $LIB/extracted ] && tar xfz $LIB.tar.gz
     touch $LIB/extracted
     BUILD_ARGS=""
+    if [[ $LIB =~ .*mercurial.* ]] 
+    then
+        PYEXE="python2.7"
+    else
+        PYEXE=${PYTHON_EXEC}
+    fi
     case $LIB in
         *h5py*)
             pushd $LIB &> /dev/null
-            ( ${DEST_DIR}/bin/python2.7 setup.py configure --hdf5=${HDF5_DIR} 2>&1 ) 1>> ${LOG_FILE} || do_exit
+            ( ${DEST_DIR}/bin/${PYTHON_EXEC} setup.py configure --hdf5=${HDF5_DIR} 2>&1 ) 1>> ${LOG_FILE} || do_exit
             popd &> /dev/null
             ;;
         *numpy*)
-            if [ -e ${DEST_DIR}/lib/python2.7/site-packages/numpy/__init__.py ]
+            if [ -e ${DEST_DIR}/lib/${PYTHON_EXEC}/site-packages/numpy/__init__.py ]
             then
-                VER=$(${DEST_DIR}/bin/python -c 'from distutils.version import StrictVersion as SV; \
+                VER=$(${DEST_DIR}/bin/${PYTHON_EXEC} -c 'from distutils.version import StrictVersion as SV; \
                                                  import numpy; print SV(numpy.__version__) < SV("1.8.0")')
                 if [ $VER == "True" ]
                 then
                     echo "Removing previous NumPy instance (see issue #889)"
-                    rm -rf ${DEST_DIR}/lib/python2.7/site-packages/{numpy*,*.pth}
+                    rm -rf ${DEST_DIR}/lib/${PYTHON_EXEC}/site-packages/{numpy*,*.pth}
                 fi
             fi
             ;;
@@ -523,8 +543,8 @@
             ;;
     esac
     cd $LIB
-    ( ${DEST_DIR}/bin/python2.7 setup.py build ${BUILD_ARGS} $* 2>&1 ) 1>> ${LOG_FILE} || do_exit
-    ( ${DEST_DIR}/bin/python2.7 setup.py install    2>&1 ) 1>> ${LOG_FILE} || do_exit
+    ( ${DEST_DIR}/bin/${PYEXE} setup.py build ${BUILD_ARGS} $* 2>&1 ) 1>> ${LOG_FILE} || do_exit
+    ( ${DEST_DIR}/bin/${PYEXE} setup.py install    2>&1 ) 1>> ${LOG_FILE} || do_exit
     touch done
     cd ..
 }
@@ -592,14 +612,15 @@
 # Set paths to what they should be when yt is activated.
 export PATH=${DEST_DIR}/bin:$PATH
 export LD_LIBRARY_PATH=${DEST_DIR}/lib:$LD_LIBRARY_PATH
-export PYTHONPATH=${DEST_DIR}/lib/python2.7/site-packages
+export PYTHONPATH=${DEST_DIR}/lib/${PYTHON_EXEC}/site-packages
 
 mkdir -p ${DEST_DIR}/src
 cd ${DEST_DIR}/src
 
+PYTHON2='Python-2.7.9'
+PYTHON3='Python-3.4.3'
 CYTHON='Cython-0.22'
 PYX='PyX-0.12.1'
-PYTHON='Python-2.7.9'
 BZLIB='bzip2-1.0.6'
 FREETYPE_VER='freetype-2.4.12' 
 H5PY='h5py-2.5.0'
@@ -620,11 +641,13 @@
 TORNADO='tornado-4.0.2'
 ZEROMQ='zeromq-4.0.5'
 ZLIB='zlib-1.2.8'
+SETUPTOOLS='setuptools-16.0'
 
 # Now we dump all our SHA512 files out.
 echo '856220fa579e272ac38dcef091760f527431ff3b98df9af6e68416fcf77d9659ac5abe5c7dee41331f359614637a4ff452033085335ee499830ed126ab584267  Cython-0.22.tar.gz' > Cython-0.22.tar.gz.sha512
 echo '4941f5aa21aff3743546495fb073c10d2657ff42b2aff401903498638093d0e31e344cce778980f28a7170c6d29eab72ac074277b9d4088376e8692dc71e55c1  PyX-0.12.1.tar.gz' > PyX-0.12.1.tar.gz.sha512
 echo 'a42f28ed8e49f04cf89e2ea7434c5ecbc264e7188dcb79ab97f745adf664dd9ab57f9a913543731635f90859536244ac37dca9adf0fc2aa1b215ba884839d160  Python-2.7.9.tgz' > Python-2.7.9.tgz.sha512
+echo '609cc82586fabecb25f25ecb410f2938e01d21cde85dd3f8824fe55c6edde9ecf3b7609195473d3fa05a16b9b121464f5414db1a0187103b78ea6edfa71684a7  Python-3.4.3.tgz' > Python-3.4.3.tgz.sha512
 echo '276bd9c061ec9a27d478b33078a86f93164ee2da72210e12e2c9da71dcffeb64767e4460b93f257302b09328eda8655e93c4b9ae85e74472869afbeae35ca71e  blas.tar.gz' > blas.tar.gz.sha512
 echo '00ace5438cfa0c577e5f578d8a808613187eff5217c35164ffe044fbafdfec9e98f4192c02a7d67e01e5a5ccced630583ad1003c37697219b0f147343a3fdd12  bzip2-1.0.6.tar.gz' > bzip2-1.0.6.tar.gz.sha512
 echo 'a296dfcaef7e853e58eed4e24b37c4fa29cfc6ac688def048480f4bb384b9e37ca447faf96eec7b378fd764ba291713f03ac464581d62275e28eb2ec99110ab6  reason-js-20120623.zip' > reason-js-20120623.zip.sha512
@@ -646,6 +669,7 @@
 echo '93591068dc63af8d50a7925d528bc0cccdd705232c529b6162619fe28dddaf115e8a460b1842877d35160bd7ed480c1bd0bdbec57d1f359085bd1814e0c1c242  tornado-4.0.2.tar.gz' > tornado-4.0.2.tar.gz.sha512
 echo '0d928ed688ed940d460fa8f8d574a9819dccc4e030d735a8c7db71b59287ee50fa741a08249e356c78356b03c2174f2f2699f05aa7dc3d380ed47d8d7bab5408  zeromq-4.0.5.tar.gz' > zeromq-4.0.5.tar.gz.sha512
 echo 'ece209d4c7ec0cb58ede791444dc754e0d10811cbbdebe3df61c0fd9f9f9867c1c3ccd5f1827f847c005e24eef34fb5bf87b5d3f894d75da04f1797538290e4a  zlib-1.2.8.tar.gz' > zlib-1.2.8.tar.gz.sha512
+echo '38a89aad89dc9aa682dbfbca623e2f69511f5e20d4a3526c01aabbc7e93ae78f20aac566676b431e111540b41540a1c4f644ce4174e7ecf052318612075e02dc  setuptools-16.0.tar.gz' > setuptools-16.0.tar.gz.sha512
 # Individual processes
 [ -z "$HDF5_DIR" ] && get_ytproject $HDF5.tar.gz
 [ $INST_ZLIB -eq 1 ] && get_ytproject $ZLIB.tar.gz
@@ -660,10 +684,11 @@
 [ $INST_SCIPY -eq 1 ] && get_ytproject $SCIPY.tar.gz
 [ $INST_SCIPY -eq 1 ] && get_ytproject blas.tar.gz
 [ $INST_SCIPY -eq 1 ] && get_ytproject $LAPACK.tar.gz
-get_ytproject $PYTHON.tgz
+[ $INST_HG -eq 1 ] && get_ytproject $MERCURIAL.tar.gz
+[ $INST_PY3 -eq 1 ] && get_ytproject $PYTHON3.tgz
+get_ytproject $PYTHON2.tgz
 get_ytproject $NUMPY.tar.gz
 get_ytproject $MATPLOTLIB.tar.gz
-get_ytproject $MERCURIAL.tar.gz
 get_ytproject $IPYTHON.tar.gz
 get_ytproject $H5PY.tar.gz
 get_ytproject $CYTHON.tar.gz
@@ -671,6 +696,7 @@
 get_ytproject $NOSE.tar.gz
 get_ytproject $PYTHON_HGLIB.tar.gz
 get_ytproject $SYMPY.tar.gz
+get_ytproject $SETUPTOOLS.tar.gz
 if [ $INST_BZLIB -eq 1 ]
 then
     if [ ! -e $BZLIB/done ]
@@ -787,11 +813,11 @@
     fi
 fi
 
-if [ ! -e $PYTHON/done ]
+if [ ! -e $PYTHON2/done ]
 then
-    echo "Installing Python.  This may take a while, but don't worry.  yt loves you."
-    [ ! -e $PYTHON ] && tar xfz $PYTHON.tgz
-    cd $PYTHON
+    echo "Installing Python 2. This may take a while, but don't worry. yt loves you."
+    [ ! -e $PYTHON2 ] && tar xfz $PYTHON2.tgz
+    cd $PYTHON2
     ( ./configure --prefix=${DEST_DIR}/ ${PYCONF_ARGS} 2>&1 ) 1>> ${LOG_FILE} || do_exit
 
     ( make ${MAKE_PROCS} 2>&1 ) 1>> ${LOG_FILE} || do_exit
@@ -802,7 +828,30 @@
     cd ..
 fi
 
-export PYTHONPATH=${DEST_DIR}/lib/python2.7/site-packages/
+if [ $INST_PY3 -eq 1 ]
+then
+    if [ ! -e $PYTHON3/done ]
+    then
+        echo "Installing Python 3. Because two Pythons are better than one."
+        [ ! -e $PYTHON3 ] && tar xfz $PYTHON3.tgz
+        cd $PYTHON3
+        ( ./configure --prefix=${DEST_DIR}/ ${PYCONF_ARGS} 2>&1 ) 1>> ${LOG_FILE} || do_exit
+
+        ( make ${MAKE_PROCS} 2>&1 ) 1>> ${LOG_FILE} || do_exit
+        ( make install 2>&1 ) 1>> ${LOG_FILE} || do_exit
+        ( ln -sf ${DEST_DIR}/bin/python3.4 ${DEST_DIR}/bin/pyyt 2>&1 ) 1>> ${LOG_FILE}
+        ( ln -sf ${DEST_DIR}/bin/python3.4 ${DEST_DIR}/bin/python 2>&1 ) 1>> ${LOG_FILE}
+        ( ln -sf ${DEST_DIR}/bin/python3-config ${DEST_DIR}/bin/python-config 2>&1 ) 1>> ${LOG_FILE}
+        ( make clean 2>&1) 1>> ${LOG_FILE} || do_exit
+        touch done
+        cd ..
+    fi
+fi
+
+export PYTHONPATH=${DEST_DIR}/lib/${PYTHON_EXEC}/site-packages/
+
+# Install setuptools
+do_setup_py $SETUPTOOLS
 
 if [ $INST_HG -eq 1 ]
 then
@@ -847,12 +896,10 @@
 
 # This fixes problems with gfortran linking.
 unset LDFLAGS
-
-echo "Installing distribute"
-( ${DEST_DIR}/bin/python2.7 ${YT_DIR}/distribute_setup.py 2>&1 ) 1>> ${LOG_FILE} || do_exit
-
+ 
 echo "Installing pip"
-( ${DEST_DIR}/bin/easy_install-2.7 pip 2>&1 ) 1>> ${LOG_FILE} || do_exit
+( ${GETFILE} https://bootstrap.pypa.io/get-pip.py 2>&1 ) 1>> ${LOG_FILE} || do_exit
+( ${DEST_DIR}/bin/${PYTHON_EXEC} get-pip.py 2>&1 ) 1>> ${LOG_FILE} || do_exit
 
 if [ $INST_SCIPY -eq 0 ]
 then
@@ -986,13 +1033,14 @@
 
 echo "Installing yt"
 [ $INST_PNG -eq 1 ] && echo $PNG_DIR > png.cfg
-( export PATH=$DEST_DIR/bin:$PATH ; ${DEST_DIR}/bin/python2.7 setup.py develop 2>&1 ) 1>> ${LOG_FILE} || do_exit
+( export PATH=$DEST_DIR/bin:$PATH ; ${DEST_DIR}/bin/${PYTHON_EXEC} setup.py develop 2>&1 ) 1>> ${LOG_FILE} || do_exit
 touch done
 cd $MY_PWD
 
-if !( ( ${DEST_DIR}/bin/python2.7 -c "import readline" 2>&1 )>> ${LOG_FILE})
+if !( ( ${DEST_DIR}/bin/${PYTHON_EXEC} -c "import readline" 2>&1 )>> ${LOG_FILE}) || \
+	[[ "${MYOS##Darwin}" != "${MYOS}" && $INST_PY3 -eq 1 ]] 
 then
-    if !( ( ${DEST_DIR}/bin/python2.7 -c "import gnureadline" 2>&1 )>> ${LOG_FILE})
+    if !( ( ${DEST_DIR}/bin/${PYTHON_EXEC} -c "import gnureadline" 2>&1 )>> ${LOG_FILE})
     then
         echo "Installing pure-python readline"
         ( ${DEST_DIR}/bin/pip install gnureadline 2>&1 ) 1>> ${LOG_FILE}

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe doc/source/analyzing/generating_processed_data.rst
--- a/doc/source/analyzing/generating_processed_data.rst
+++ b/doc/source/analyzing/generating_processed_data.rst
@@ -47,10 +47,30 @@
    frb = FixedResolutionBuffer(sl, (0.3, 0.5, 0.6, 0.8), (512, 512))
    my_image = frb["density"]
 
-This resultant array can be saved out to disk or visualized using a
-hand-constructed Matplotlib image, for instance using
+This image may then be used in a hand-constructed Matplotlib image, for instance using
 :func:`~matplotlib.pyplot.imshow`.
 
+The buffer arrays can be saved out to disk in either HDF5 or FITS format:
+ 
+.. code-block:: python
+
+   frb.export_hdf5("my_images.h5", fields=["density","temperature"])
+   frb.export_fits("my_images.fits", fields=["density","temperature"],
+                   clobber=True, units="kpc")
+
+In the FITS case, there is an option for setting the ``units`` of the coordinate system in
+the file. If you want to overwrite a file with the same name, set ``clobber=True``. 
+
+The :class:`~yt.visualization.fixed_resolution.FixedResolutionBuffer` can even be exported
+as a 2D dataset itself, which may be operated on in the same way as any other dataset in yt:
+
+.. code-block:: python
+
+   ds_frb = frb.export_dataset(fields=["density","temperature"], nprocs=8)
+   sp = ds_frb.sphere("c", (100.,"kpc"))
+
+where the ``nprocs`` parameter can be used to decompose the image into ``nprocs`` number of grids.
+
 .. _generating-profiles-and-histograms:
 
 Profiles and Histograms

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe setup.py
--- a/setup.py
+++ b/setup.py
@@ -13,11 +13,6 @@
     sys.exit(1)
 
 import setuptools
-from distutils.version import StrictVersion
-if StrictVersion(setuptools.__version__) < StrictVersion('0.7.0'):
-    import distribute_setup
-    distribute_setup.use_setuptools()
-
 from distutils.command.build_py import build_py
 from numpy.distutils.misc_util import appendpath
 from numpy.distutils.command import install_data as np_install_data

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/analysis_modules/absorption_spectrum/absorption_line.py
--- a/yt/analysis_modules/absorption_spectrum/absorption_line.py
+++ b/yt/analysis_modules/absorption_spectrum/absorption_line.py
@@ -16,12 +16,9 @@
 import numpy as np
 from yt.utilities.physical_constants import \
     charge_proton_cgs, \
-    cm_per_km, \
-    km_per_cm, \
     mass_electron_cgs, \
     speed_of_light_cgs
 
-
 def voigt(a,u):
     """
     NAME:
@@ -140,67 +137,75 @@
     k1 = k1.astype(np.float64).clip(0)
     return k1
 
-def tau_profile(lam0, fval, gamma, vkms, column_density, 
-                deltav=None, delta_lambda=None,
+def tau_profile(lamba_0, f_value, gamma, v_doppler, column_density, 
+                delta_v=None, delta_lambda=None,
                 lambda_bins=None, n_lambda=12000, dlambda=0.01):
-    """
+    r"""
     Create an optical depth vs. wavelength profile for an 
     absorption line using a voigt profile.
-    :param lam0 (float): central wavelength (angstroms).
-    :param fval (float): f-value.
-    :param gamma (float): gamma value.
-    :param vkms (float): doppler b-parameter.
-    :param column_density (float): column density (cm^-2).
-    :param deltav (float): velocity offset from lam0 (km/s).
-    Default: None (no shift).
-    :param delta_lambda (float): wavelength offset in angstroms.
-    Default: None (no shift).
-    :param lambda_bins (array): array of wavelengths in angstroms.
-    Default: None
-    :param n_lambda (float): size of lambda bins to create 
-    array if lambda_bins is None.  Default: 12000
-    :param dlambda (float): lambda bin width if lambda_bins is 
-    None. Default: 0.01
+
+    Parameters
+    ----------
+    
+    lamba_0 : float YTQuantity in length units
+       central wavelength.
+    f_value : float
+       absorption line f-value.
+    gamma : float
+       absorption line gamma value.
+    v_doppler : float YTQuantity in velocity units
+       doppler b-parameter.
+    column_density : float YTQuantity in (length units)^-2
+       column density.
+    delta_v : float YTQuantity in velocity units
+       velocity offset from lamba_0.
+       Default: None (no shift).
+    delta_lambda : float YTQuantity in length units
+        wavelength offset.
+        Default: None (no shift).
+    lambda_bins : YTArray in length units
+        wavelength array for line deposition.  If None, one will be 
+        created using n_lambda and dlambda.
+        Default: None.
+    n_lambda : int
+        size of lambda bins to create if lambda_bins is None.
+        Default: 12000.
+    dlambda : float 
+        lambda bin width in angstroms if lambda_bins is None.
+        Default: 0.01.
+        
     """
 
-    ## constants
-    me = mass_electron_cgs              # grams mass electron 
-    e = charge_proton_cgs               # esu 
-    c = speed_of_light_cgs * km_per_cm  # km/s
-    ccgs = speed_of_light_cgs           # cm/s 
-
-    ## shift lam0 by deltav
-    if deltav is not None:
-        lam1 = lam0 * (1 + deltav / c)
+    ## shift lamba_0 by delta_v
+    if delta_v is not None:
+        lam1 = lamba_0 * (1 + delta_v / speed_of_light_cgs)
     elif delta_lambda is not None:
-        lam1 = lam0 + delta_lambda
+        lam1 = lamba_0 + delta_lambda
     else:
-        lam1 = lam0
+        lam1 = lamba_0
 
     ## conversions
-    vdop = vkms * cm_per_km           # in cm/s
-    lam0cgs = lam0 / 1.e8             # rest wavelength in cm
-    lam1cgs = lam1 / 1.e8             # line wavelength in cm
-    nu1 = ccgs / lam1cgs              # line freq in Hz
-    nudop = vdop / ccgs * nu1         # doppler width in Hz
-    lamdop = vdop / ccgs * lam1       # doppler width in Ang
+    nu1 = speed_of_light_cgs / lam1           # line freq in Hz
+    nudop = v_doppler / speed_of_light_cgs * nu1   # doppler width in Hz
+    lamdop = v_doppler / speed_of_light_cgs * lam1 # doppler width in Ang
 
     ## create wavelength
     if lambda_bins is None:
         lambda_bins = lam1 + \
             np.arange(n_lambda, dtype=np.float) * dlambda - \
-            n_lambda * dlambda / 2    # wavelength vector (angstroms)
-    nua = ccgs / (lambda_bins / 1.e8) # frequency vector (Hz)
+            n_lambda * dlambda / 2  # wavelength vector (angstroms)
+    nua = (speed_of_light_cgs / lambda_bins)  # frequency vector (Hz)
 
     ## tau_0
-    tau_X = np.sqrt(np.pi) * e**2 / (me * ccgs) * \
-        column_density * fval / vdop
-    tau0 = tau_X * lam0cgs
+    tau_X = np.sqrt(np.pi) * charge_proton_cgs**2 / \
+      (mass_electron_cgs * speed_of_light_cgs) * \
+      column_density * f_value / v_doppler
+    tau0 = tau_X * lamba_0
 
     # dimensionless frequency offset in units of doppler freq
-    x = (nua - nu1) / nudop
-    a = gamma / (4 * np.pi * nudop)   # damping parameter 
-    phi = voigt(a, x)                 # profile
-    tauphi = tau0 * phi               # profile scaled with tau0
+    x = ((nua - nu1) / nudop).in_units("")
+    a = (gamma / (4 * np.pi * nudop)).in_units("s")  # damping parameter 
+    phi = voigt(a, x)                                # line profile
+    tauphi = (tau0 * phi).in_units("")               # profile scaled with tau0
 
     return (lambda_bins, tauphi)

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/analysis_modules/absorption_spectrum/absorption_spectrum.py
--- a/yt/analysis_modules/absorption_spectrum/absorption_spectrum.py
+++ b/yt/analysis_modules/absorption_spectrum/absorption_spectrum.py
@@ -4,7 +4,7 @@
 
 
 """
-from __future__ import print_function
+
 from __future__ import absolute_import
 
 #-----------------------------------------------------------------------------
@@ -21,13 +21,12 @@
 from .absorption_line import tau_profile
 
 from yt.funcs import get_pbar, mylog
-from yt.units.yt_array import YTArray
+from yt.units.yt_array import YTArray, YTQuantity
 from yt.utilities.physical_constants import \
-    amu_cgs, boltzmann_constant_cgs, \
-    speed_of_light_cgs, km_per_cm
+    boltzmann_constant_cgs, \
+    speed_of_light_cgs
 from yt.utilities.on_demand_imports import _astropy
 
-speed_of_light_kms = speed_of_light_cgs * km_per_cm
 pyfits = _astropy.pyfits
 
 class AbsorptionSpectrum(object):
@@ -49,8 +48,10 @@
         self.tau_field = None
         self.flux_field = None
         self.spectrum_line_list = None
-        self.lambda_bins = np.linspace(lambda_min, lambda_max, n_lambda)
-        self.bin_width = (lambda_max - lambda_min) / float(n_lambda - 1)
+        self.lambda_bins = YTArray(np.linspace(lambda_min, lambda_max, n_lambda),
+                                   "angstrom")
+        self.bin_width = YTQuantity((lambda_max - lambda_min) / 
+                                    float(n_lambda - 1), "angstrom")
         self.line_list = []
         self.continuum_list = []
 
@@ -76,8 +77,10 @@
            mass of atom in amu.
         """
         self.line_list.append({'label': label, 'field_name': field_name,
-                               'wavelength': wavelength, 'f_value': f_value,
-                               'gamma': gamma, 'atomic_mass': atomic_mass,
+                               'wavelength': YTQuantity(wavelength, "angstrom"),
+                               'f_value': f_value,
+                               'gamma': gamma,
+                               'atomic_mass': YTQuantity(atomic_mass, "amu"),
                                'label_threshold': label_threshold})
 
     def add_continuum(self, label, field_name, wavelength,
@@ -209,16 +212,15 @@
                 # include factor of (1 + z) because our velocity is in proper frame.
                 delta_lambda += line['wavelength'] * (1 + field_data['redshift']) * \
                     field_data['velocity_los'] / speed_of_light_cgs
-            thermal_b = km_per_cm * np.sqrt((2 * boltzmann_constant_cgs *
-                                             field_data['temperature']) /
-                                            (amu_cgs * line['atomic_mass']))
-            thermal_b.convert_to_cgs()
+            thermal_b =  np.sqrt((2 * boltzmann_constant_cgs *
+                                  field_data['temperature']) /
+                                  line['atomic_mass'])
             center_bins = np.digitize((delta_lambda + line['wavelength']),
                                       self.lambda_bins)
 
             # ratio of line width to bin width
             width_ratio = ((line['wavelength'] + delta_lambda) * \
-                thermal_b / speed_of_light_kms / self.bin_width).value
+                           thermal_b / speed_of_light_cgs / self.bin_width).in_units("").d
 
             if (width_ratio < 1.0).any():
                 mylog.warn(("%d out of %d line components are unresolved, " +
@@ -240,11 +242,13 @@
                 my_bin_ratio = spectrum_bin_ratio
                 while True:
                     lambda_bins, line_tau = \
-                        tau_profile(line['wavelength'], line['f_value'],
-                                    line['gamma'], thermal_b[lixel],
-                                    column_density[lixel],
-                                    delta_lambda=delta_lambda[lixel],
-                                    lambda_bins=self.lambda_bins[left_index[lixel]:right_index[lixel]])
+                        tau_profile(
+                            line['wavelength'], line['f_value'],
+                            line['gamma'], thermal_b[lixel].in_units("km/s"),
+                            column_density[lixel],
+                            delta_lambda=delta_lambda[lixel],
+                            lambda_bins=self.lambda_bins[left_index[lixel]:right_index[lixel]])
+                        
                     # Widen wavelength window until optical depth reaches a max value at the ends.
                     if (line_tau[0] < max_tau and line_tau[-1] < max_tau) or \
                       (left_index[lixel] <= 0 and right_index[lixel] >= self.n_lambda):
@@ -260,7 +264,7 @@
                 if line['label_threshold'] is not None and \
                         column_density[lixel] >= line['label_threshold']:
                     if use_peculiar_velocity:
-                        peculiar_velocity = km_per_cm * field_data['velocity_los'][lixel]
+                        peculiar_velocity = field_data['velocity_los'][lixel].in_units("km/s")
                     else:
                         peculiar_velocity = 0.0
                     self.spectrum_line_list.append({'label': line['label'],
@@ -271,7 +275,7 @@
                                                     'redshift': field_data['redshift'][lixel],
                                                     'v_pec': peculiar_velocity})
                     pbar.update(i)
-            pbar.finish()
+                pbar.finish()
 
             del column_density, delta_lambda, thermal_b, \
                 center_bins, width_ratio, left_index, right_index
@@ -280,7 +284,7 @@
         """
         Write out list of spectral lines.
         """
-        print("Writing spectral line list: %s." % filename)
+        mylog.info("Writing spectral line list: %s." % filename)
         self.spectrum_line_list.sort(key=lambda obj: obj['wavelength'])
         f = open(filename, 'w')
         f.write('#%-14s %-14s %-12s %-12s %-12s %-12s\n' %
@@ -295,7 +299,7 @@
         """
         Write spectrum to an ascii file.
         """
-        print("Writing spectrum to ascii file: %s." % filename)
+        mylog.info("Writing spectrum to ascii file: %s." % filename)
         f = open(filename, 'w')
         f.write("# wavelength[A] tau flux\n")
         for i in range(self.lambda_bins.size):
@@ -307,7 +311,7 @@
         """
         Write spectrum to a fits file.
         """
-        print("Writing spectrum to fits file: %s." % filename)
+        mylog.info("Writing spectrum to fits file: %s." % filename)
         col1 = pyfits.Column(name='wavelength', format='E', array=self.lambda_bins)
         col2 = pyfits.Column(name='flux', format='E', array=self.flux_field)
         cols = pyfits.ColDefs([col1, col2])
@@ -319,7 +323,7 @@
         Write spectrum to an hdf5 file.
 
         """
-        print("Writing spectrum to hdf5 file: %s." % filename)
+        mylog.info("Writing spectrum to hdf5 file: %s." % filename)
         output = h5py.File(filename, 'w')
         output.create_dataset('wavelength', data=self.lambda_bins)
         output.create_dataset('tau', data=self.tau_field)

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/analysis_modules/absorption_spectrum/absorption_spectrum_fit.py
--- a/yt/analysis_modules/absorption_spectrum/absorption_spectrum_fit.py
+++ b/yt/analysis_modules/absorption_spectrum/absorption_spectrum_fit.py
@@ -1,9 +1,14 @@
-from __future__ import print_function
+import h5py
 import numpy as np
-import h5py
-from yt.analysis_modules.absorption_spectrum.absorption_line \
-        import voigt
-from yt.utilities.on_demand_imports import _scipy
+
+from yt.analysis_modules.absorption_spectrum.absorption_line import \
+    voigt
+from yt.funcs import \
+    mylog
+from yt.units.yt_array import \
+    YTArray
+from yt.utilities.on_demand_imports import \
+    _scipy
 
 optimize = _scipy.optimize
 
@@ -79,6 +84,10 @@
         absorption profiles. Same size as x.
     """
 
+    # convert to NumPy array if we have a YTArray
+    if isinstance(x, YTArray):
+        x = x.d
+    
     #Empty dictionary for fitted lines
     allSpeciesLines = {}
 
@@ -1007,6 +1016,5 @@
         f.create_dataset("{0}/b".format(ion),data=params['b'])
         f.create_dataset("{0}/z".format(ion),data=params['z'])
         f.create_dataset("{0}/complex".format(ion),data=params['group#'])
-    print('Writing spectrum fit to {0}'.format(file_name))
+    mylog.info('Writing spectrum fit to {0}'.format(file_name))
     f.close()
-

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/frontends/stream/data_structures.py
--- a/yt/frontends/stream/data_structures.py
+++ b/yt/frontends/stream/data_structures.py
@@ -709,7 +709,7 @@
             pdata = pdata_ftype
         # This will update the stream handler too
         assign_particle_data(sds, pdata)
-    
+
     return sds
 
 def load_amr_grids(grid_data, domain_dimensions,

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/visualization/base_plot_types.py
--- a/yt/visualization/base_plot_types.py
+++ b/yt/visualization/base_plot_types.py
@@ -54,6 +54,7 @@
             self._type_name = "CuttingPlane"
         else:
             self._type_name = viewer._plot_type
+        self.aspect = window_plot._aspect
         self.font_properties = font_properties
         self.font_color = font_color
 

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/visualization/fixed_resolution.py
--- a/yt/visualization/fixed_resolution.py
+++ b/yt/visualization/fixed_resolution.py
@@ -20,6 +20,7 @@
 from yt.utilities.lib.pixelization_routines import \
     pixelize_cylinder
 from yt.utilities.lib.api import add_points_to_greyscale_image
+from yt.frontends.stream.api import load_uniform_grid
 
 from . import _MPL
 import numpy as np
@@ -73,13 +74,13 @@
     To make a projection and then several images, you can generate a
     single FRB and then access multiple fields:
 
-    >>> proj = ds.proj(0, "Density")
+    >>> proj = ds.proj(0, "density")
     >>> frb1 = FixedResolutionBuffer(proj, (0.2, 0.3, 0.4, 0.5),
-                    (1024, 1024))
-    >>> print frb1["Density"].max()
-    1.0914e-9
-    >>> print frb1["Temperature"].max()
-    104923.1
+    ...                              (1024, 1024))
+    >>> print frb1["density"].max()
+    1.0914e-9 g/cm**3
+    >>> print frb1["temperature"].max()
+    104923.1 K
     """
     _exclude_fields = ('pz','pdz','dx','x','y','z',
         'r', 'dr', 'phi', 'dphi', 'theta', 'dtheta',
@@ -289,7 +290,7 @@
             These fields will be pixelized and output.
         """
         import h5py
-        if fields is None: fields = self.data.keys()
+        if fields is None: fields = list(self.data.keys())
         output = h5py.File(filename, "a")
         for field in fields:
             output.create_dataset(field,data=self[field])
@@ -307,30 +308,68 @@
         filename : string
             The name of the FITS file to be written.
         fields : list of strings
-            These fields will be pixelized and output.
+            These fields will be pixelized and output. If "None", the keys of the
+            FRB will be used. 
         clobber : boolean
             If the file exists, this governs whether we will overwrite.
         other_keys : dictionary, optional
             A set of header keys and values to write into the FITS header.
         units : string, optional
-            the length units that the coordinates are written in, default 'cm'
-            If units are set to "deg" then assume that sky coordinates are
-            requested.
+            the length units that the coordinates are written in, default 'cm'.
         """
 
         from yt.utilities.fits_image import FITSImageData
 
-        extra_fields = ['x','y','z','px','py','pz','pdx','pdy','pdz','weight_field']
-        if fields is None: 
-            fields = [field[-1] for field in self.data_source.field_data
-                      if field not in extra_fields]
+        if fields is None: fields = list(self.data.keys())
 
         fib = FITSImageData(self, fields=fields, units=units)
         if other_keys is not None:
             for k,v in other_keys.items():
                 fib.update_all_headers(k,v)
         fib.writeto(filename, clobber=clobber)
-        
+
+    def export_dataset(self, fields=None, nprocs=1):
+        r"""Export a set of pixelized fields to an in-memory dataset that can be
+        analyzed as any other in yt. Unit information and other parameters (e.g., 
+        geometry, current_time, etc.) will be taken from the parent dataset. 
+
+        Parameters
+        ----------
+        fields : list of strings, optional
+            These fields will be pixelized and output. If "None", the keys of the
+            FRB will be used. 
+        nprocs: integer, optional
+            If greater than 1, will create this number of subarrays out of data
+
+        Examples
+        --------
+        >>> import yt
+        >>> ds = yt.load("GasSloshing/sloshing_nomag2_hdf5_plt_cnt_0150")
+        >>> slc = ds.slice(2, 0.0)
+        >>> frb = slc.to_frb((500.,"kpc"), 500)
+        >>> ds2 = frb.export_dataset(fields=["density","temperature"], nprocs=32)
+        """
+        nx, ny = self.buff_size
+        data = {}
+        if fields is None:
+            fields = list(self.keys())
+        for field in fields:
+            arr = self[field]
+            data[field] = (arr.d.T.reshape(nx,ny,1), str(arr.units))
+        bounds = [b.in_units("code_length").v for b in self.bounds]
+        bbox = np.array([[bounds[0],bounds[1]],[bounds[2],bounds[3]],[0.,1.]])
+        return load_uniform_grid(data, [nx,ny,1],
+                                 length_unit=self.ds.length_unit,
+                                 bbox=bbox,
+                                 sim_time=self.ds.current_time.in_units("s").v,
+                                 mass_unit=self.ds.mass_unit,
+                                 time_unit=self.ds.time_unit,
+                                 velocity_unit=self.ds.velocity_unit,
+                                 magnetic_unit=self.ds.magnetic_unit,
+                                 periodicity=(False,False,False),
+                                 geometry=self.ds.geometry,
+                                 nprocs=nprocs)
+
     @property
     def limits(self):
         rv = dict(x = None, y = None, z = None)

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/visualization/plot_container.py
--- a/yt/visualization/plot_container.py
+++ b/yt/visualization/plot_container.py
@@ -14,7 +14,9 @@
 #-----------------------------------------------------------------------------
 from yt.extern.six.moves import builtins
 from yt.extern.six import iteritems
+
 import base64
+import errno
 import numpy as np
 import matplotlib
 import os
@@ -536,7 +538,13 @@
             name = str(self.ds)
         name = os.path.expanduser(name)
         if name[-1] == os.sep and not os.path.isdir(name):
-            os.mkdir(name)
+            try:
+                os.mkdir(name)
+            except OSError as e:
+                if e.errno == errno.EEXIST:
+                    pass
+                else:
+                    raise
         if os.path.isdir(name) and name != str(self.ds):
             name = name + (os.sep if name[-1] != os.sep else '') + str(self.ds)
         if suffix is None:

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/visualization/plot_modifications.py
--- a/yt/visualization/plot_modifications.py
+++ b/yt/visualization/plot_modifications.py
@@ -23,6 +23,7 @@
 
 from matplotlib.patches import Circle
 from matplotlib.colors import colorConverter
+from mpl_toolkits.axes_grid1.anchored_artists import AnchoredSizeBar
 
 from yt.funcs import *
 from yt.extern.six import add_metaclass
@@ -1665,11 +1666,11 @@
         # Setting pos overrides corner argument
         if self.pos[0] is None or self.pos[1] is None:
             if self.corner == 'upper_left':
-                self.pos = (0.03, 0.97)
+                self.pos = (0.03, 0.96)
                 self.text_args['horizontalalignment'] = 'left'
                 self.text_args['verticalalignment'] = 'top'
             elif self.corner == 'upper_right':
-                self.pos = (0.97, 0.97)
+                self.pos = (0.97, 0.96)
                 self.text_args['horizontalalignment'] = 'right'
                 self.text_args['verticalalignment'] = 'top'
             elif self.corner == 'lower_left':
@@ -1726,47 +1727,49 @@
 class ScaleCallback(PlotCallback):
     """
     annotate_scale(corner='lower_right', coeff=None, unit=None, pos=None,
-                   max_frac=0.2, min_frac=0.018, coord_system='axis',
-                   text_args=None, plot_args=None)
+                   max_frac=0.16, min_frac=0.015, coord_system='axis',
+                   size_bar_args=None, draw_inset_box=False, 
+                   inset_box_args=None)
 
     Annotates the scale of the plot at a specified location in the image
     (either in a preset corner, or by specifying (x,y) image coordinates with
-    the pos argument.  Coeff and units (e.g. 1 Mpc or 100 kpc) refer to the 
-    distance scale you desire to show on the plot.  If no coeff and units are 
-    specified, an appropriate pair will be determined such that your scale bar 
-    is never smaller than min_frac or greater than max_frac of your plottable 
-    axis length.  For additional text and plot arguments for the text and line,
-    include them as dictionaries to pass to text_args and plot_args.
-    
+    the pos argument.  Coeff and units (e.g. 1 Mpc or 100 kpc) refer to the
+    distance scale you desire to show on the plot.  If no coeff and units are
+    specified, an appropriate pair will be determined such that your scale bar
+    is never smaller than min_frac or greater than max_frac of your plottable
+    axis length.  Additional customization of the scale bar is possible by
+    adjusting the size_bar_args dictionary.  This accepts keyword arguments
+    for the AnchoredSizeBar class in matplotlib's axes_grid toolkit.
+
     Parameters
     ----------
 
     corner : string, optional
-        Corner sets up one of 4 predeterimined locations for the timestamp
+        Corner sets up one of 4 predeterimined locations for the scale bar
         to be displayed in the image: 'upper_left', 'upper_right', 'lower_left',
-        'lower_right' (also allows None). This value will be overridden by the 
+        'lower_right' (also allows None). This value will be overridden by the
         optional 'pos' keyword.
 
     coeff : float, optional
         The coefficient of the unit defining the distance scale (e.g. 10 kpc or
-        100 Mpc) for overplotting.  If set to None along with unit keyword, 
+        100 Mpc) for overplotting.  If set to None along with unit keyword,
         coeff will be automatically determined to be a power of 10
         relative to the best-fit unit.
 
     unit : string, optional
-        unit must be a valid yt distance unit (e.g. 'm', 'km', 'AU', 'pc', 
+        unit must be a valid yt distance unit (e.g. 'm', 'km', 'AU', 'pc',
         'kpc', etc.) or set to None.  If set to None, will be automatically
         determined to be the best-fit to the data.
 
     pos : 2- or 3-element tuples, lists, or arrays, optional
-        The image location of the timestamp in the coord system defined by the
-        coord_system kwarg.  Setting pos overrides the corner parameter.
+        The image location of the scale bar in the plot coordinate system.
+        Setting pos overrides the corner parameter.
 
     min_frac, max_frac: float, optional
-        The minimum/maximum fraction of the axis width for the scale bar to 
+        The minimum/maximum fraction of the axis width for the scale bar to
         extend. A value of 1 would allow the scale bar to extend across the
-        entire axis width.  Only used for automatically calculating 
-        best-fit coeff and unit when neither is specified, otherwise 
+        entire axis width.  Only used for automatically calculating
+        best-fit coeff and unit when neither is specified, otherwise
         disregarded.
 
     coord_system : string, optional
@@ -1783,17 +1786,23 @@
             "figure" -- the MPL figure coordinates: (0,0) is lower left, (1,1)
                         is upper right
 
-    text_args : dictionary, optional
-        A dictionary of any arbitrary parameters to be passed to the Matplotlib
-        text object.  Defaults: {'color':'white', 
-        'horizontalalignment':'center', 'verticalalignment':'top'}.
+    size_bar_args : dictionary, optional
+        A dictionary of parameters to be passed to the Matplotlib
+        AnchoredSizeBar initializer.
+        Defaults: {'pad': 0.25, 'sep': 5, 'borderpad': 1, 'color': 'w'}
 
-    plot_args : dictionary, optional
-        A dictionary of any arbitrary parameters to be passed to the Matplotlib
-        line object.  Defaults: {'color':'white', 'linewidth':3}.
+    draw_inset_box : boolean, optional
+        Whether or not an inset box should be included around the scale bar.
+
+    inset_box_args : dictionary, optional
+        A dictionary of keyword arguments to be passed to the matplotlib Patch
+        object that represents the inset box.
+        Defaults: {'facecolor': 'black', 'linewidth': 3, 'edgecolor', 'white',
+                   'alpha': 0.5, 'boxstyle': 'square'}
+
 
     Example
-    ------- 
+    -------
 
     >>> import yt
     >>> ds = yt.load('Enzo_64/DD0020/data0020')
@@ -1802,11 +1811,23 @@
     """
     _type_name = "scale"
     def __init__(self, corner='lower_right', coeff=None, unit=None, pos=None, 
-                 max_frac=0.20, min_frac=0.018, coord_system='axis',
-                 text_args=None, plot_args=None):
+                 max_frac=0.16, min_frac=0.015, coord_system='axis',
+                 size_bar_args=None, draw_inset_box=False, inset_box_args=None):
 
-        def_text_args = {'color':'white'}
-        def_plot_args = {'color':'white', 'linewidth':3}
+        def_size_bar_args = {
+            'pad': 0.05,
+            'sep': 5,
+            'borderpad': 1,
+            'color': 'w'
+        }
+
+        inset_box_args = {
+            'facecolor': 'black',
+            'linewidth': 3,
+            'edgecolor': 'white',
+            'alpha': 0.5,
+            'boxstyle': 'square',
+        }
 
         # Set position based on corner argument.
         self.corner = corner
@@ -1816,33 +1837,34 @@
         self.max_frac = max_frac
         self.min_frac = min_frac
         self.coord_system = coord_system
-        if text_args is None: text_args = def_text_args
-        self.text_args = text_args
-        # This assures the line and the text are aligned
-        self.text_args['horizontalalignment'] = 'center'
-        self.text_args['verticalalignment'] = 'top'
-        if plot_args is None: plot_args = def_plot_args
-        self.plot_args = plot_args
+        if size_bar_args is None:
+            self.size_bar_args = def_size_bar_args
+        else:
+            self.size_bar_args = size_bar_args
+        if inset_box_args is None:
+            self.inset_box_args = def_inset_box_args
+        else:
+            self.inset_box_args = inset_box_args
+        self.draw_inset_box = draw_inset_box
 
     def __call__(self, plot):
         # Callback only works for plots with axis ratios of 1
         xsize = plot.xlim[1] - plot.xlim[0]
-        ysize = plot.ylim[1] - plot.ylim[0]
-        if xsize != ysize:
-            raise RuntimeError("Scale callback only works for plots with "
-                               "axis ratios of 1. Here: xsize = %s, ysize "
-                               " = %s." % (xsize, ysize))
+        if plot.aspect != 1.0:
+            raise NotImplementedError(
+                "Scale callback has only been implemented for plots with no "
+                "aspect ratio scaling. (aspect = {%s})".format(plot._aspect))
 
         # Setting pos overrides corner argument
         if self.pos is None:
             if self.corner == 'upper_left':
-                self.pos = (0.12, 0.971)
+                self.pos = (0.11, 0.952)
             elif self.corner == 'upper_right':
-                self.pos = (0.88, 0.971)
+                self.pos = (0.89, 0.952)
             elif self.corner == 'lower_left':
-                self.pos = (0.12, 0.062)
+                self.pos = (0.11, 0.052)
             elif self.corner == 'lower_right':
-                self.pos = (0.88, 0.062)
+                self.pos = (0.89, 0.052)
             elif self.corner is None:
                 self.pos = (0.5, 0.5)
             else:
@@ -1851,8 +1873,8 @@
                                   "'lower_right', or None")
 
         # When identifying a best fit distance unit, do not allow scale marker
-        # to be greater than max_frac fraction of xaxis or under min_frac 
-        # fraction of xaxis 
+        # to be greater than max_frac fraction of xaxis or under min_frac
+        # fraction of xaxis
         max_scale = self.max_frac * xsize
         min_scale = self.min_frac * xsize
 
@@ -1861,30 +1883,38 @@
 
         # If no units are set, then identify a best fit distance unit
         if self.unit is None:
-            min_scale = plot.ds.get_smallest_appropriate_unit(min_scale, 
-                                                   return_quantity=True)
-            max_scale = plot.ds.get_smallest_appropriate_unit(max_scale, 
-                                                   return_quantity=True)
+            min_scale = plot.ds.get_smallest_appropriate_unit(
+                min_scale, return_quantity=True)
+            max_scale = plot.ds.get_smallest_appropriate_unit(
+                max_scale, return_quantity=True)
             self.coeff = max_scale.v
             self.unit = max_scale.units
         self.scale = YTQuantity(self.coeff, self.unit)
-        self.text = "{scale} {units}".format(scale=int(self.coeff), 
-                                             units=self.unit)
-        image_scale = (plot.frb.convert_distance_x(self.scale) / \
+        text = "{scale} {units}".format(scale=int(self.coeff), units=self.unit)
+        image_scale = (plot.frb.convert_distance_x(self.scale) /
                        plot.frb.convert_distance_x(xsize)).v
 
-        # This is just a fancy wrapper around the TextLabelCallback and the
-        # ImageLineCallback
-        pos_line_start = (self.pos[0]-image_scale/2, self.pos[1]+0.01)
-        pos_line_end = (self.pos[0]+image_scale/2, self.pos[1]+0.01)
-        icb = LinePlotCallback(pos_line_start, pos_line_end, 
-                               coord_system=self.coord_system, 
-                               plot_args=self.plot_args)
-        icb(plot)
-        tcb = TextLabelCallback(self.pos, self.text, 
-                                coord_system=self.coord_system,
-                                text_args=self.text_args)
-        return tcb(plot)
+        size_vertical = self.size_bar_args.pop('size_vertical', .005)
+        fontproperties = self.size_bar_args.pop(
+            'fontproperties', plot.font_properties)
+        frameon = self.size_bar_args.pop('frameon', self.draw_inset_box)
+
+        # this "anchors" the size bar to a box centered on self.pos in axis
+        # coordinates
+        self.size_bar_args['bbox_to_anchor'] = self.pos
+        self.size_bar_args['bbox_transform'] = plot._axes.transAxes
+
+        bar = AnchoredSizeBar(plot._axes.transAxes, image_scale, text, 10,
+                              size_vertical=size_vertical,
+                              fontproperties=fontproperties,
+                              frameon=frameon,
+                              **self.size_bar_args)
+
+        bar.patch.set(**self.inset_box_args)
+
+        plot._axes.add_artist(bar)
+
+        return plot
 
 class RayCallback(PlotCallback):
     """

diff -r 16985637841f11d9bb814ad0f2edcc9391cbcf60 -r 45467416f055ff41bac76b5d90f392e5f0f5cafe yt/visualization/tests/test_export_frb.py
--- /dev/null
+++ b/yt/visualization/tests/test_export_frb.py
@@ -0,0 +1,39 @@
+"""
+Tests for exporting an FRB as a dataset
+
+
+
+"""
+from __future__ import absolute_import
+
+#-----------------------------------------------------------------------------
+# Copyright (c) 2013, yt Development Team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file COPYING.txt, distributed with this software.
+#-----------------------------------------------------------------------------
+import numpy as np
+from yt.testing import \
+    fake_random_ds, assert_equal, \
+    assert_allclose
+
+def setup():
+    """Test specific setup."""
+    from yt.config import ytcfg
+    ytcfg["yt", "__withintesting"] = "True"
+
+
+def test_export_frb():
+    test_ds = fake_random_ds(128)
+    slc = test_ds.slice(0,0.5)
+    frb = slc.to_frb((0.5,"unitary"), 64)
+    frb_ds = frb.export_dataset(fields=["density"], nprocs=8)
+    dd_frb = frb_ds.all_data()
+
+    yield assert_equal, frb_ds.domain_left_edge.v, np.array([0.25,0.25,0.0])
+    yield assert_equal, frb_ds.domain_right_edge.v, np.array([0.75,0.75,1.0])
+    yield assert_equal, frb_ds.domain_width.v, np.array([0.5,0.5,1.0])
+    yield assert_equal, frb_ds.domain_dimensions, np.array([64,64,1], dtype="int64")
+    yield assert_allclose, frb["density"].sum(), dd_frb.quantities.total_quantity("density")
+    yield assert_equal, frb_ds.index.num_grids, 8


https://bitbucket.org/yt_analysis/yt/commits/a8be9a38fde1/
Changeset:   a8be9a38fde1
Branch:      yt
User:        jzuhone
Date:        2015-06-03 16:47:01+00:00
Summary:     Replacing this here as well
Affected #:  1 file

diff -r 45467416f055ff41bac76b5d90f392e5f0f5cafe -r a8be9a38fde15f42a2aec4d2bac7015b03a85ec8 yt/frontends/fits/misc.py
--- a/yt/frontends/fits/misc.py
+++ b/yt/frontends/fits/misc.py
@@ -18,7 +18,7 @@
 from yt.funcs import mylog, get_image_suffix
 from yt.visualization._mpl_imports import FigureCanvasAgg
 from yt.units.yt_array import YTQuantity, YTArray
-from yt.utilities.fits_image import FITSImageBuffer
+from yt.utilities.fits_image import FITSImageData
 
 import os
 
@@ -127,7 +127,7 @@
     w = subcube.wcs.copy()
     w.wcs.crpix[-1] = 0.5
     w.wcs.crval[-1] = -0.5*width
-    fid = FITSImageBuffer(slab_data, wcs=w)
+    fid = FITSImageData(slab_data, wcs=w)
     for hdu in fid:
         hdu.header.pop("RESTFREQ", None)
         hdu.header.pop("RESTFRQ", None)


https://bitbucket.org/yt_analysis/yt/commits/2ab401515cc1/
Changeset:   2ab401515cc1
Branch:      yt
User:        jzuhone
Date:        2015-06-11 21:39:58+00:00
Summary:     Fixing a few things noticed by Matt
Affected #:  2 files

diff -r a8be9a38fde15f42a2aec4d2bac7015b03a85ec8 -r 2ab401515cc14a74d47d79ff9f0a788aa15241a7 yt/analysis_modules/ppv_cube/ppv_cube.py
--- a/yt/analysis_modules/ppv_cube/ppv_cube.py
+++ b/yt/analysis_modules/ppv_cube/ppv_cube.py
@@ -312,8 +312,8 @@
 
     def _create_intensity(self):
         def _intensity(field, data):
-            v = self.current_v-data["v_los"].v
-            T = data["temperature"].v
+            v = self.current_v-data["v_los"].in_cgs().v
+            T = (data["temperature"]).in_cgs().v
             w = ppv_utils.compute_weight(self.thermal_broad, self.dv_cgs,
                                          self.particle_mass, v.flatten(), T.flatten())
             w[np.isnan(w)] = 0.0

diff -r a8be9a38fde15f42a2aec4d2bac7015b03a85ec8 -r 2ab401515cc14a74d47d79ff9f0a788aa15241a7 yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -163,7 +163,7 @@
                 if isinstance(width[0], YTQuantity):
                     cdelt = [wh.in_units(units).v/n for wh, n in zip(width, self.shape)]
                 else:
-                    cdelt = [wh/n for wh, n in zip(width, self.shape)]
+                    cdelt = [float(wh)/n for wh, n in zip(width, self.shape)]
                 center = [0.0]*self.dimensionality
             w.wcs.crpix = 0.5*(np.array(self.shape)+1)
             w.wcs.crval = center
@@ -429,7 +429,7 @@
         width = ds.coordinates.sanitize_width(axis, width, None)
         unit = str(width[0].units)
     if image_res is None:
-        ddims = ds.domain_dimensions*2**ds.index.max_level
+        ddims = ds.domain_dimensions*ds.refine_by**ds.index.max_level
         if iterable(axis):
             nx = ddims.max()
             ny = ddims.max()


https://bitbucket.org/yt_analysis/yt/commits/e4bc6b4f239b/
Changeset:   e4bc6b4f239b
Branch:      yt
User:        xarthisius
Date:        2015-06-18 13:17:28+00:00
Summary:     Merged in jzuhone/yt (pull request #1603)

FITS image writing refactor
Affected #:  12 files

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f doc/source/visualizing/FITSImageBuffer.ipynb
--- a/doc/source/visualizing/FITSImageBuffer.ipynb
+++ /dev/null
@@ -1,205 +0,0 @@
-{
- "metadata": {
-  "name": "",
-  "signature": "sha256:872f7525edd3c1ee09c67f6ecdd8552218df05ebe5ab73bcab55654edf0ac2bb"
- },
- "nbformat": 3,
- "nbformat_minor": 0,
- "worksheets": [
-  {
-   "cells": [
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "yt has capabilities for writing 2D and 3D uniformly gridded data generated from datasets to FITS files. This is via the `FITSImageBuffer` class, which has subclasses `FITSSlice` and `FITSProjection` to write slices and projections directly to FITS. We'll test this out on an Athena dataset."
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "%matplotlib inline\n",
-      "import yt\n",
-      "from yt.utilities.fits_image import FITSImageBuffer, FITSSlice, FITSProjection"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "ds = yt.load(\"MHDSloshing/virgo_low_res.0054.vtk\", parameters={\"length_unit\":(1.0,\"Mpc\"),\n",
-      "                                                               \"mass_unit\":(1.0e14,\"Msun\"),\n",
-      "                                                               \"time_unit\":(1.0,\"Myr\")})"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "To demonstrate a useful example of creating a FITS file, let's first make a `ProjectionPlot`:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj = yt.ProjectionPlot(ds, \"z\", [\"temperature\"], weight_field=\"density\", width=(500.,\"kpc\"))\n",
-      "prj.show()"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Suppose that we wanted to write this projection to a FITS file for analysis and visualization in other programs, such as ds9. We can do that using `FITSProjection`:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits = FITSProjection(ds, \"z\", [\"temperature\"], weight_field=\"density\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "which took the same parameters as `ProjectionPlot` except the width, because `FITSProjection` and `FITSSlice` always make slices and projections of the width of the domain size, at the finest resolution available in the simulation, in a unit determined to be appropriate for the physical size of the dataset. `prj_fits` is a full-fledged FITS file in memory, specifically an [AstroPy `HDUList`](http://astropy.readthedocs.org/en/latest/io/fits/api/hdulists.html) object. This means that we can use all of the methods inherited from `HDUList`:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits.info()"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "`info` shows us the contents of the virtual FITS file. We can also look at the header for the `\"temperature\"` image, like so:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits[\"temperature\"].header"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "where we can see that the temperature units are in Kelvin and the cell widths are in kiloparsecs. The projection can be written to disk using the `writeto` method:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "prj_fits.writeto(\"sloshing.fits\", clobber=True)"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Since yt can read FITS image files, it can be loaded up just like any other dataset:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "ds2 = yt.load(\"sloshing.fits\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "and we can make a `SlicePlot` of the 2D image, which shows the same data as the previous image:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "slc2 = yt.SlicePlot(ds2, \"z\", [\"temperature\"], width=(500.,\"kpc\"))\n",
-      "slc2.set_log(\"temperature\", True)\n",
-      "slc2.show()"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "If you want more fine-grained control over what goes into the FITS file, you can call `FITSImageBuffer` directly, with various kinds of inputs. For example, you could use a `FixedResolutionBuffer`, and specify you want the units in parsecs instead:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "slc3 = ds.slice(0, 0.0)\n",
-      "frb = slc3.to_frb((500.,\"kpc\"), 800)\n",
-      "fib = FITSImageBuffer(frb, fields=[\"density\",\"temperature\"], units=\"pc\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    },
-    {
-     "cell_type": "markdown",
-     "metadata": {},
-     "source": [
-      "Finally, a 3D FITS cube can be created from a covering grid:"
-     ]
-    },
-    {
-     "cell_type": "code",
-     "collapsed": false,
-     "input": [
-      "cvg = ds.covering_grid(ds.index.max_level, [-0.5,-0.5,-0.5], [64, 64, 64], fields=[\"density\",\"temperature\"])\n",
-      "fib = FITSImageBuffer(cvg, fields=[\"density\",\"temperature\"], units=\"Mpc\")"
-     ],
-     "language": "python",
-     "metadata": {},
-     "outputs": []
-    }
-   ],
-   "metadata": {}
-  }
- ]
-}
\ No newline at end of file

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f doc/source/visualizing/FITSImageData.ipynb
--- /dev/null
+++ b/doc/source/visualizing/FITSImageData.ipynb
@@ -0,0 +1,409 @@
+{
+ "metadata": {
+  "name": "",
+  "signature": "sha256:c7de5ef190feaa2289595aec7eaa05db02fd535e408e0d04aa54088b0bd3ebae"
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "yt has capabilities for writing 2D and 3D uniformly gridded data generated from datasets to FITS files. This is via the `FITSImageData` class. We'll test these capabilities out on an Athena dataset."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "import yt\n",
+      "from yt.utilities.fits_image import FITSImageData, FITSProjection"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "ds = yt.load(\"MHDSloshing/virgo_low_res.0054.vtk\", parameters={\"length_unit\":(1.0,\"Mpc\"),\n",
+      "                                                               \"mass_unit\":(1.0e14,\"Msun\"),\n",
+      "                                                               \"time_unit\":(1.0,\"Myr\")})"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Creating FITS images from Slices and Projections"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "There are several ways to make a `FITSImageData` instance. The most intuitive ways are to use the `FITSSlice`, `FITSProjection`, `FITSOffAxisSlice`, and `FITSOffAxisProjection` classes to write slices and projections directly to FITS. To demonstrate a useful example of creating a FITS file, let's first make a `ProjectionPlot`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj = yt.ProjectionPlot(ds, \"z\", [\"temperature\"], weight_field=\"density\", width=(500.,\"kpc\"))\n",
+      "prj.show()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Suppose that we wanted to write this projection to a FITS file for analysis and visualization in other programs, such as ds9. We can do that using `FITSProjection`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits = FITSProjection(ds, \"z\", [\"temperature\"], weight_field=\"density\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "which took the same parameters as `ProjectionPlot` except the width, because `FITSProjection` and `FITSSlice` always make slices and projections of the width of the domain size, at the finest resolution available in the simulation, in a unit determined to be appropriate for the physical size of the dataset."
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Because `FITSImageData` inherits from the [AstroPy `HDUList`](http://astropy.readthedocs.org/en/latest/io/fits/api/hdulists.html) class, we can call its methods. For example, `info` shows us the contents of the virtual FITS file:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "We can also look at the header for a particular field:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits[\"temperature\"].header"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "where we can see that the temperature units are in Kelvin and the cell widths are in kiloparsecs. If we want the raw image data with units, we can call `get_data`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.get_data(\"temperature\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "We can use the `set_unit` method to change the units of a particular field:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.set_unit(\"temperature\",\"R\")\n",
+      "prj_fits.get_data(\"temperature\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "The image can be written to disk using the `writeto` method:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits.writeto(\"sloshing.fits\", clobber=True)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Since yt can read FITS image files, it can be loaded up just like any other dataset:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "ds2 = yt.load(\"sloshing.fits\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "and we can make a `SlicePlot` of the 2D image, which shows the same data as the previous image:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "slc2 = yt.SlicePlot(ds2, \"z\", [\"temperature\"], width=(500.,\"kpc\"))\n",
+      "slc2.set_log(\"temperature\", True)\n",
+      "slc2.show()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Using `FITSImageData` directly"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "If you want more fine-grained control over what goes into the FITS file, you can call `FITSImageData` directly, with various kinds of inputs. For example, you could use a `FixedResolutionBuffer`, and specify you want the units in parsecs instead:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "slc3 = ds.slice(0, 0.0)\n",
+      "frb = slc3.to_frb((500.,\"kpc\"), 800)\n",
+      "fid_frb = FITSImageData(frb, fields=[\"density\",\"temperature\"], units=\"pc\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "A 3D FITS cube can also be created from a covering grid:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "cvg = ds.covering_grid(ds.index.max_level, [-0.5,-0.5,-0.5], [64, 64, 64], fields=[\"density\",\"temperature\"])\n",
+      "fid_cvg = FITSImageData(cvg, fields=[\"density\",\"temperature\"], units=\"Mpc\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Other `FITSImageData` Methods"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "A `FITSImageData` instance can be generated from one previously written to disk using the `from_file` classmethod:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "fid = FITSImageData.from_file(\"sloshing.fits\")\n",
+      "fid.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Multiple `FITSImageData` can be combined to create a new one, provided that the coordinate information is the same:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits2 = FITSProjection(ds, \"z\", [\"density\"])\n",
+      "prj_fits3 = FITSImageData.from_images([prj_fits, prj_fits2])\n",
+      "prj_fits3.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Alternatively, individual fields can be popped as well:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "dens_fits = prj_fits3.pop(\"density\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "dens_fits.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits3.info()"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "So far, the FITS images we have shown have linear spatial coordinates. One may want to take a projection of an object and make a crude mock observation out of it, with celestial coordinates. For this, we can use the `create_sky_wcs` method. Specify a center (RA, Dec) coordinate in degrees, as well as a linear scale in terms of angle per distance:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "sky_center = [30.,45.] # in degrees\n",
+      "sky_scale = (2.5, \"arcsec/kpc\") # could also use a YTQuantity\n",
+      "prj_fits.create_sky_wcs(sky_center, sky_scale, ctype=[\"RA---TAN\",\"DEC--TAN\"])"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "By the default, a tangent RA/Dec projection is used, but one could also use another projection using the `ctype` keyword. We can now look at the header and see it has the appropriate WCS:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "prj_fits[\"temperature\"].header"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Finally, we can add header keywords to a single field or for all fields in the FITS image using `update_header`:"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "fid_frb.update_header(\"all\", \"time\", 0.1) # Update all the fields\n",
+      "fid_frb.update_header(\"temperature\", \"scale\", \"Rankine\") # Update just one field"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "print fid_frb[\"density\"].header[\"time\"]\n",
+      "print fid_frb[\"temperature\"].header[\"scale\"]"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
\ No newline at end of file

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f doc/source/visualizing/writing_fits_images.rst
--- a/doc/source/visualizing/writing_fits_images.rst
+++ b/doc/source/visualizing/writing_fits_images.rst
@@ -3,4 +3,4 @@
 Writing FITS Images
 ==========================
 
-.. notebook:: FITSImageBuffer.ipynb
\ No newline at end of file
+.. notebook:: FITSImageData.ipynb
\ No newline at end of file

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/analysis_modules/ppv_cube/ppv_cube.py
--- a/yt/analysis_modules/ppv_cube/ppv_cube.py
+++ b/yt/analysis_modules/ppv_cube/ppv_cube.py
@@ -13,8 +13,7 @@
 import numpy as np
 from yt.utilities.on_demand_imports import _astropy
 from yt.utilities.orientation import Orientation
-from yt.utilities.fits_image import FITSImageBuffer, sanitize_fits_unit, \
-    create_sky_wcs
+from yt.utilities.fits_image import FITSImageData, sanitize_fits_unit
 from yt.visualization.volume_rendering.camera import off_axis_projection
 from yt.funcs import get_pbar
 from yt.utilities.physical_constants import clight, mh
@@ -89,6 +88,8 @@
         dims : integer, optional
             The spatial resolution of the cube. Implies nx = ny, e.g. the 
             aspect ratio of the PPVCube's spatial dimensions is 1.
+        thermal_broad : boolean, optional
+            Whether or not to broaden the line using the gas temperature. Default: False.
         atomic_weight : float, optional
             Set this value to the atomic weight of the particle that is emitting the line
             if *thermal_broad* is True. Defaults to 56 (Fe).
@@ -152,9 +153,7 @@
                                "methods are supported in PPVCube.")
 
         dd = ds.all_data()
-
         fd = dd._determine_fields(field)[0]
-
         self.field_units = ds._get_field_info(fd).units
 
         self.vbins = ds.arr(np.linspace(velocity_bounds[0],
@@ -172,7 +171,7 @@
         _vlos = create_vlos(normal, self.no_shifting)
         self.ds.add_field(("gas","v_los"), function=_vlos, units="cm/s")
 
-        _intensity = self.create_intensity()
+        _intensity = self._create_intensity()
         self.ds.add_field(("gas","intensity"), function=_intensity, units=self.field_units)
 
         if method == "integrate" and weight_field is None:
@@ -214,16 +213,6 @@
         self.ds.field_info.pop(("gas","intensity"))
         self.ds.field_info.pop(("gas","v_los"))
 
-    def create_intensity(self):
-        def _intensity(field, data):
-            v = self.current_v-data["v_los"].v
-            T = data["temperature"].v
-            w = ppv_utils.compute_weight(self.thermal_broad, self.dv_cgs,
-                                         self.particle_mass, v.flatten(), T.flatten())
-            w[np.isnan(w)] = 0.0
-            return data[self.field]*w.reshape(v.shape)
-        return _intensity
-
     def transform_spectral_axis(self, rest_value, units):
         """
         Change the units of the spectral axis to some equivalent unit, such
@@ -259,17 +248,18 @@
         self.dv = self.vbins[1]-self.vbins[0]
 
     @parallel_root_only
-    def write_fits(self, filename, clobber=True, length_unit=None,
+    def write_fits(self, filename, clobber=False, length_unit=None,
                    sky_scale=None, sky_center=None):
         r""" Write the PPVCube to a FITS file.
 
         Parameters
         ----------
         filename : string
-            The name of the file to write.
-        clobber : boolean
-            Whether or not to clobber an existing file with the same name.
-        length_unit : string
+            The name of the file to write to. 
+        clobber : boolean, optional
+            Whether to overwrite a file with the same name that already 
+            exists. Default False.
+        length_unit : string, optional
             The units to convert the coordinates to in the file.
         sky_scale : tuple, optional
             Conversion between an angle unit and a length unit, if sky
@@ -280,7 +270,8 @@
 
         Examples
         --------
-        >>> cube.write_fits("my_cube.fits", clobber=False, sky_scale=(1.0,"arcsec/kpc"))
+        >>> cube.write_fits("my_cube.fits", clobber=False, 
+        ...                 sky_scale=(1.0,"arcsec/kpc"), sky_center=(30.,45.))
         """
         vunit = fits_info[self.axis_type][0]
         vtype = fits_info[self.axis_type][1]
@@ -303,13 +294,11 @@
         w.wcs.cunit = [units,units,vunit]
         w.wcs.ctype = ["LINEAR","LINEAR",vtype]
 
+        fib = FITSImageData(self.data.transpose(), fields=self.field, wcs=w)
+        fib.update_all_headers("bunit", re.sub('()', '', str(self.proj_units)))
+        fib.update_all_headers("btype", self.field)
         if sky_scale is not None and sky_center is not None:
-            w = create_sky_wcs(w, sky_center, sky_scale)
-
-        fib = FITSImageBuffer(self.data.transpose(), fields=self.field, wcs=w)
-        fib[0].header["bunit"] = re.sub('()', '', str(self.proj_units))
-        fib[0].header["btype"] = self.field
-
+            fib.create_sky_wcs(sky_center, sky_scale)
         fib.writeto(filename, clobber=clobber)
 
     def __repr__(self):
@@ -320,3 +309,13 @@
 
     def __getitem__(self, item):
         return self.data[item]
+
+    def _create_intensity(self):
+        def _intensity(field, data):
+            v = self.current_v-data["v_los"].in_cgs().v
+            T = (data["temperature"]).in_cgs().v
+            w = ppv_utils.compute_weight(self.thermal_broad, self.dv_cgs,
+                                         self.particle_mass, v.flatten(), T.flatten())
+            w[np.isnan(w)] = 0.0
+            return data[self.field]*w.reshape(v.shape)
+        return _intensity

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/analysis_modules/ppv_cube/tests/test_ppv.py
--- a/yt/analysis_modules/ppv_cube/tests/test_ppv.py
+++ b/yt/analysis_modules/ppv_cube/tests/test_ppv.py
@@ -1,5 +1,5 @@
 """
-Unit test the sunyaev_zeldovich analysis module.
+Unit test the PPVCube analysis module.
 """
 
 #-----------------------------------------------------------------------------

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/analysis_modules/sunyaev_zeldovich/projection.py
--- a/yt/analysis_modules/sunyaev_zeldovich/projection.py
+++ b/yt/analysis_modules/sunyaev_zeldovich/projection.py
@@ -316,7 +316,7 @@
         >>> sky_center = (30., 45., "deg")
         >>> szprj.write_fits("SZbullet.fits", sky_center=sky_center, sky_scale=sky_scale)
         """
-        from yt.utilities.fits_image import FITSImageBuffer, create_sky_wcs
+        from yt.utilities.fits_image import FITSImageData
 
         dx = self.dx.in_units("kpc")
         dy = dx
@@ -328,10 +328,9 @@
         w.wcs.cunit = ["kpc"]*2
         w.wcs.ctype = ["LINEAR"]*2
 
+        fib = FITSImageData(self.data, fields=self.data.keys(), wcs=w)
         if sky_scale is not None and sky_center is not None:
-            w = create_sky_wcs(w, sky_center, sky_scale)
-
-        fib = FITSImageBuffer(self.data, fields=self.data.keys(), wcs=w)
+            fib.create_sky_wcs(sky_center, sky_scale)
         fib.writeto(filename, clobber=clobber)
         
     @parallel_root_only

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/frontends/fits/misc.py
--- a/yt/frontends/fits/misc.py
+++ b/yt/frontends/fits/misc.py
@@ -18,7 +18,7 @@
 from yt.funcs import mylog, get_image_suffix
 from yt.visualization._mpl_imports import FigureCanvasAgg
 from yt.units.yt_array import YTQuantity, YTArray
-from yt.utilities.fits_image import FITSImageBuffer
+from yt.utilities.fits_image import FITSImageData
 
 import os
 
@@ -127,7 +127,7 @@
     w = subcube.wcs.copy()
     w.wcs.crpix[-1] = 0.5
     w.wcs.crval[-1] = -0.5*width
-    fid = FITSImageBuffer(slab_data, wcs=w)
+    fid = FITSImageData(slab_data, wcs=w)
     for hdu in fid:
         hdu.header.pop("RESTFREQ", None)
         hdu.header.pop("RESTFRQ", None)

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/utilities/fits_image.py
--- a/yt/utilities/fits_image.py
+++ b/yt/utilities/fits_image.py
@@ -1,5 +1,5 @@
 """
-FITSImageBuffer Class
+FITSImageData Class
 """
 
 #-----------------------------------------------------------------------------
@@ -16,6 +16,10 @@
 from yt.data_objects.construction_data_containers import YTCoveringGridBase
 from yt.utilities.on_demand_imports import _astropy, NotAModule
 from yt.units.yt_array import YTQuantity, YTArray
+from yt.units import dimensions
+from yt.utilities.parallel_tools.parallel_analysis_interface import \
+    parallel_root_only
+from yt.visualization.volume_rendering.camera import off_axis_projection
 import re
 
 pyfits = _astropy.pyfits
@@ -26,18 +30,17 @@
 else:
     HDUList = pyfits.HDUList
 
-class FITSImageBuffer(HDUList):
+class FITSImageData(HDUList):
 
-    def __init__(self, data, fields=None, units=None, pixel_scale=None, wcs=None):
-        r""" Initialize a FITSImageBuffer object.
+    def __init__(self, data, fields=None, units=None, width=None, wcs=None):
+        r""" Initialize a FITSImageData object.
 
-        FITSImageBuffer contains a list of FITS ImageHDU instances, and
-        optionally includes WCS information. It inherits from HDUList, so
-        operations such as `writeto` are enabled. Images can be constructed
-        from ImageArrays, NumPy arrays, dicts of such arrays,
-        FixedResolutionBuffers, and YTCoveringGrids. The latter two are the
-        most powerful because WCS information can be constructed from their
-        coordinates.
+        FITSImageData contains a collection of FITS ImageHDU instances and
+        WCS information, along with units for each of the images. FITSImageData
+        instances can be constructed from ImageArrays, NumPy arrays, dicts 
+        of such arrays, FixedResolutionBuffers, and YTCoveringGrids. The latter 
+        two are the most powerful because WCS information can be constructed 
+        automatically from their coordinates.
 
         Parameters
         ----------
@@ -50,10 +53,10 @@
             single array one field name must be specified.
         units : string
             The units of the WCS coordinates. Defaults to "cm".
-        pixel_scale : float
-            The scale of the pixel, in *units*. Either a single float or
-            iterable of floats. Only used if this information is not already
-            provided by *data*.
+        width : float or YTQuantity
+            The width of the image. Either a single value or iterable of values.
+            If a float, assumed to be in *units*. Only used if this information 
+            is not already provided by *data*.
         wcs : `astropy.wcs.WCS` instance, optional
             Supply an AstroPy WCS instance. Will override automatic WCS
             creation from FixedResolutionBuffers and YTCoveringGrids.
@@ -66,7 +69,7 @@
         >>> prj = ds.proj(2, "kT", weight_field="density")
         >>> frb = prj.to_frb((0.5, "Mpc"), 800)
         >>> # This example just uses the FRB and puts the coords in kpc.
-        >>> f_kpc = FITSImageBuffer(frb, fields="kT", units="kpc")
+        >>> f_kpc = FITSImageData(frb, fields="kT", units="kpc")
         >>> # This example specifies a specific WCS.
         >>> from astropy.wcs import WCS
         >>> w = WCS(naxis=self.dimensionality)
@@ -77,46 +80,52 @@
         >>> w.wcs.ctype = ["RA---TAN","DEC--TAN"]
         >>> scale = 1./3600. # One arcsec per pixel
         >>> w.wcs.cdelt = [-scale, scale]
-        >>> f_deg = FITSImageBuffer(frb, fields="kT", wcs=w)
+        >>> f_deg = FITSImageData(frb, fields="kT", wcs=w)
         >>> f_deg.writeto("temp.fits")
         """
 
-        if units is None: units = "cm"
-        if pixel_scale is None: pixel_scale = 1.0
+        if units is None:
+            units = "cm"
+        if width is None:
+            width = 1.0
 
-        super(FITSImageBuffer, self).__init__()
+        exclude_fields = ['x','y','z','px','py','pz',
+                          'pdx','pdy','pdz','weight_field']
+
+        super(FITSImageData, self).__init__()
 
         if isinstance(fields, string_types):
             fields = [fields]
 
-        exclude_fields = ['x', 'y', 'z', 'px', 'py', 'pz',
-                          'pdx', 'pdy', 'pdz', 'weight_field']
-
         if hasattr(data, 'keys'):
             img_data = data
-        else:
-            img_data = {}
             if fields is None:
-                mylog.error("Please specify a field name for this array.")
-                raise KeyError("Please specify a field name for this array.")
-            img_data[fields[0]] = data
+                fields = list(img_data.keys())
+        elif isinstance(data, np.ndarray):
+            if fields is None:
+                mylog.warning("No field name given for this array. Calling it 'image_data'.")
+                fn = 'image_data'
+                fields = [fn]
+            else:
+                fn = fields[0]
+            img_data = {fn: data}
 
-        if fields is None: fields = img_data.keys()
-        if len(fields) == 0:
-            mylog.error("Please specify one or more fields to write.")
-            raise KeyError("Please specify one or more fields to write.")
+        self.fields = []
+        for fd in fields:
+            if isinstance(fd, tuple):
+                self.fields.append(fd[1])
+            else:
+                self.fields.append(fd)
 
         first = True
-
         self.field_units = {}
-
         for key in fields:
             if key not in exclude_fields:
                 if hasattr(img_data[key], "units"):
                     self.field_units[key] = str(img_data[key].units)
                 else:
                     self.field_units[key] = "dimensionless"
-                mylog.info("Making a FITS image of field %s" % (key))
+                mylog.info("Making a FITS image of field %s" % key)
                 if first:
                     hdu = pyfits.PrimaryHDU(np.array(img_data[key]))
                     first = False
@@ -128,12 +137,8 @@
                     hdu.header["bunit"] = re.sub('()', '', str(img_data[key].units))
                 self.append(hdu)
 
-        self.dimensionality = len(self[0].data.shape)
-        
-        if self.dimensionality == 2:
-            self.nx, self.ny = self[0].data.shape
-        elif self.dimensionality == 3:
-            self.nx, self.ny, self.nz = self[0].data.shape
+        self.shape = self[0].shape
+        self.dimensionality = len(self.shape)
 
         if wcs is None:
             w = pywcs.WCS(header=self[0].header, naxis=self.dimensionality)
@@ -141,22 +146,24 @@
                 # FRBs are a special case where we have coordinate
                 # information, so we take advantage of this and
                 # construct the WCS object
-                dx = (img_data.bounds[1]-img_data.bounds[0]).in_units(units)/self.nx
-                dy = (img_data.bounds[3]-img_data.bounds[2]).in_units(units)/self.ny
-                xctr = 0.5*(img_data.bounds[1]+img_data.bounds[0]).in_units(units)
-                yctr = 0.5*(img_data.bounds[3]+img_data.bounds[2]).in_units(units)
+                dx = (img_data.bounds[1]-img_data.bounds[0]).in_units(units).v/self.shape[0]
+                dy = (img_data.bounds[3]-img_data.bounds[2]).in_units(units).v/self.shape[1]
+                xctr = 0.5*(img_data.bounds[1]+img_data.bounds[0]).in_units(units).v
+                yctr = 0.5*(img_data.bounds[3]+img_data.bounds[2]).in_units(units).v
                 center = [xctr, yctr]
                 cdelt = [dx,dy]
             elif isinstance(img_data, YTCoveringGridBase):
                 cdelt = img_data.dds.in_units(units).v
-                center = 0.5*(img_data.left_edge+img_data.right_edge).in_units(units)
+                center = 0.5*(img_data.left_edge+img_data.right_edge).in_units(units).v
             else:
                 # If img_data is just an array, we assume the center is the origin
-                # and use *pixel_scale* to determine the cell widths
-                if iterable(pixel_scale):
-                    cdelt = pixel_scale
+                # and use the image width to determine the cell widths
+                if not iterable(width):
+                    width = [width]*self.dimensionality
+                if isinstance(width[0], YTQuantity):
+                    cdelt = [wh.in_units(units).v/n for wh, n in zip(width, self.shape)]
                 else:
-                    cdelt = [pixel_scale]*self.dimensionality
+                    cdelt = [float(wh)/n for wh, n in zip(width, self.shape)]
                 center = [0.0]*self.dimensionality
             w.wcs.crpix = 0.5*(np.array(self.shape)+1)
             w.wcs.crval = center
@@ -178,53 +185,79 @@
             for k, v in h.items():
                 img.header[k] = v
 
+    def update_header(self, field, key, value):
+        """
+        Update the FITS header for *field* with a
+        *key*, *value* pair. If *field* == "all", all 
+        headers will be updated.
+        """
+        if field == "all":
+            for img in self:
+                img.header[key] = value
+        else:
+            if field not in self.keys():
+                raise KeyError("%s not an image!" % field)
+            idx = self.fields.index(field)
+            self[idx].header[key] = value
+
     def update_all_headers(self, key, value):
-        """
-        Update the FITS headers for all images with the
-        same *key*, *value* pair.
-        """
-        for img in self: img.header[key] = value
+        mylog.warning("update_all_headers is deprecated. "+
+                      "Use update_header('all', key, value) instead.")
+        self.update_header("all", key, value)
 
     def keys(self):
-        return [f.name.lower() for f in self]
+        return self.fields
 
     def has_key(self, key):
-        return key in self.keys()
+        return key in self.fields
 
     def values(self):
-        return [self[k] for k in self.keys()]
+        return [self[k] for k in self.fields]
 
     def items(self):
-        return [(k, self[k]) for k in self.keys()]
+        return [(k, self[k]) for k in self.fields]
 
-    def writeto(self, fileobj, **kwargs):
-        pyfits.HDUList(self).writeto(fileobj, **kwargs)
+    @parallel_root_only
+    def writeto(self, fileobj, fields=None, clobber=False, **kwargs):
+        r"""
+        Write all of the fields or a subset of them to a FITS file. 
 
-    @property
-    def shape(self):
-        if self.dimensionality == 2:
-            return self.nx, self.ny
-        elif self.dimensionality == 3:
-            return self.nx, self.ny, self.nz
+        Parameters
+        ----------
+        fileobj : string
+            The name of the file to write to. 
+        fields : list of strings, optional
+            The fields to write to the file. If not specified
+            all of the fields in the buffer will be written.
+        clobber : boolean, optional
+            Whether or not to overwrite a previously existing file.
+            Default: False
+        All other keyword arguments are passed to the `writeto`
+        method of `astropy.io.fits.HDUList`.
+        """
+        if fields is None:
+            hdus = pyfits.HDUList(self)
+        else:
+            hdus = pyfits.HDUList()
+            for field in fields:
+                hdus.append(self[field])
+        hdus.writeto(fileobj, clobber=clobber, **kwargs)
 
     def to_glue(self, label="yt", data_collection=None):
         """
-        Takes the data in the FITSImageBuffer and exports it to
-        Glue (http://www.glueviz.org) for interactive
-        analysis. Optionally add a *label*. If you are already within
-        the Glue environment, you can pass a *data_collection* object,
-        otherwise Glue will be started.
+        Takes the data in the FITSImageData instance and exports it to
+        Glue (http://www.glueviz.org) for interactive analysis. Optionally 
+        add a *label*. If you are already within the Glue environment, you 
+        can pass a *data_collection* object, otherwise Glue will be started.
         """
         from glue.core import DataCollection, Data
         from glue.core.coordinates import coordinates_from_header
         from glue.qt.glue_application import GlueApplication
 
-        field_dict = dict((key,self[key].data) for key in self.keys())
-        
         image = Data(label=label)
         image.coords = coordinates_from_header(self.wcs.to_header())
-        for k,v in field_dict.items():
-            image.add_component(v, k)
+        for k,f in self.items():
+            image.add_component(f.data, k)
         if data_collection is None:
             dc = DataCollection([image])
             app = GlueApplication(dc)
@@ -242,64 +275,139 @@
         return aplpy.FITSFigure(self, **kwargs)
 
     def get_data(self, field):
+        """
+        Return the data array of the image corresponding to *field*
+        with units attached.
+        """
         return YTArray(self[field].data, self.field_units[field])
 
     def set_unit(self, field, units):
         """
         Set the units of *field* to *units*.
         """
-        new_data = YTArray(self[field].data, self.field_units[field]).in_units(units)
-        self[field].data = new_data.v
-        self[field].header["bunit"] = units
+        if field not in self.keys():
+            raise KeyError("%s not an image!" % field)
+        idx = self.fields.index(field)
+        new_data = YTArray(self[idx].data, self.field_units[field]).in_units(units)
+        self[idx].data = new_data.v
+        self[idx].header["bunit"] = units
         self.field_units[field] = units
 
-axis_wcs = [[1,2],[0,2],[0,1]]
+    def pop(self, key):
+        """
+        Remove a field with name *key*
+        and return it as a new FITSImageData 
+        instance.
+        """
+        if key not in self.keys():
+            raise KeyError("%s not an image!" % key)
+        idx = self.fields.index(key)
+        im = super(FITSImageData, self).pop(idx)
+        data = YTArray(im.data, self.field_units[key])
+        self.field_units.pop(key)
+        self.fields.remove(key)
+        return FITSImageData(data, fields=key, wcs=self.wcs)
 
-def create_sky_wcs(old_wcs, sky_center, sky_scale,
-                   ctype=["RA---TAN","DEC--TAN"], crota=None):
-    """
-    Takes an astropy.wcs.WCS instance created in yt from a
-    simulation that has a Cartesian coordinate system and
-    converts it to one in a celestial coordinate system.
+    @classmethod
+    def from_file(cls, filename):
+        """
+        Generate a FITSImageData instance from one previously written to 
+        disk.
 
-    Parameters
-    ----------
-    old_wcs : astropy.wcs.WCS
-        The original WCS to be converted.
-    sky_center : tuple
-        Reference coordinates of the WCS in degrees.
-    sky_scale : tuple
-        Conversion between an angle unit and a length unit,
-        e.g. (3.0, "arcsec/kpc")
-    ctype : list of strings, optional
-        The type of the coordinate system to create.
-    crota : list of floats, optional
-        Rotation angles between cartesian coordinates and
-        the celestial coordinates.
-    """
-    naxis = old_wcs.naxis
-    crval = [sky_center[0], sky_center[1]]
-    scaleq = YTQuantity(sky_scale[0],sky_scale[1])
-    deltas = old_wcs.wcs.cdelt
-    units = [str(unit) for unit in old_wcs.wcs.cunit]
-    new_dx = (YTQuantity(-deltas[0], units[0])*scaleq).in_units("deg")
-    new_dy = (YTQuantity(deltas[1], units[1])*scaleq).in_units("deg")
-    new_wcs = pywcs.WCS(naxis=naxis)
-    cdelt = [new_dx.v, new_dy.v]
-    cunit = ["deg"]*2
-    if naxis == 3:
-        crval.append(old_wcs.wcs.crval[2])
-        cdelt.append(old_wcs.wcs.cdelt[2])
-        ctype.append(old_wcs.wcs.ctype[2])
-        cunit.append(old_wcs.wcs.cunit[2])
-    new_wcs.wcs.crpix = old_wcs.wcs.crpix
-    new_wcs.wcs.cdelt = cdelt
-    new_wcs.wcs.crval = crval
-    new_wcs.wcs.cunit = cunit
-    new_wcs.wcs.ctype = ctype
-    if crota is not None:
-        new_wcs.wcs.crota = crota
-    return new_wcs
+        Parameters
+        ----------
+        filename : string
+            The name of the file to open.
+        """
+        f = pyfits.open(filename)
+        data = {}
+        for hdu in f:
+            data[hdu.header["btype"]] = YTArray(hdu.data, hdu.header["bunit"])
+        f.close()
+        return cls(data, wcs=pywcs.WCS(header=hdu.header))
+
+    @classmethod
+    def from_images(cls, image_list):
+        """
+        Generate a new FITSImageData instance from a list of FITSImageData 
+        instances.
+
+        Parameters
+        ----------
+        image_list : list of FITSImageData instances
+            The images to be combined.
+        """
+        w = image_list[0].wcs
+        img_shape = image_list[0].shape
+        data = {}
+        for image in image_list:
+            assert_same_wcs(w, image.wcs)
+            if img_shape != image.shape:
+                raise RuntimeError("Images do not have the same shape!")
+            for key in image.keys():
+                data[key] = image.get_data(key)
+        return cls(data, wcs=w)
+
+    def create_sky_wcs(self, sky_center, sky_scale,
+                       ctype=["RA---TAN","DEC--TAN"],
+                       crota=None, cd=None, pc=None):
+        """
+        Takes a Cartesian WCS and converts it to one in a
+        celestial coordinate system.
+
+        Parameters
+        ----------
+        sky_center : iterable of floats
+            Reference coordinates of the WCS in degrees.
+        sky_scale : tuple or YTQuantity
+            Conversion between an angle unit and a length unit,
+            e.g. (3.0, "arcsec/kpc")
+        ctype : list of strings, optional
+            The type of the coordinate system to create.
+        crota : 2-element ndarray, optional
+            Rotation angles between cartesian coordinates and
+            the celestial coordinates.
+        cd : 2x2-element ndarray, optional
+            Dimensioned coordinate transformation matrix.
+        pc : 2x2-element ndarray, optional
+            Coordinate transformation matrix.
+        """
+        old_wcs = self.wcs
+        naxis = old_wcs.naxis
+        crval = [sky_center[0], sky_center[1]]
+        if isinstance(sky_scale, YTQuantity):
+            scaleq = sky_scale
+        else:
+            scaleq = YTQuantity(sky_scale[0],sky_scale[1])
+        if scaleq.units.dimensions != dimensions.angle/dimensions.length:
+            raise RuntimeError("sky_scale %s not in correct dimensions of angle/length!" % sky_scale)
+        deltas = old_wcs.wcs.cdelt
+        units = [str(unit) for unit in old_wcs.wcs.cunit]
+        new_dx = (YTQuantity(-deltas[0], units[0])*scaleq).in_units("deg")
+        new_dy = (YTQuantity(deltas[1], units[1])*scaleq).in_units("deg")
+        new_wcs = pywcs.WCS(naxis=naxis)
+        cdelt = [new_dx.v, new_dy.v]
+        cunit = ["deg"]*2
+        if naxis == 3:
+            crval.append(old_wcs.wcs.crval[2])
+            cdelt.append(old_wcs.wcs.cdelt[2])
+            ctype.append(old_wcs.wcs.ctype[2])
+            cunit.append(old_wcs.wcs.cunit[2])
+        new_wcs.wcs.crpix = old_wcs.wcs.crpix
+        new_wcs.wcs.cdelt = cdelt
+        new_wcs.wcs.crval = crval
+        new_wcs.wcs.cunit = cunit
+        new_wcs.wcs.ctype = ctype
+        if crota is not None:
+            new_wcs.wcs.crota = crota
+        if cd is not None:
+            new_wcs.wcs.cd = cd
+        if pc is not None:
+            new_wcs.wcs.cd = pc
+        self.set_wcs(new_wcs)
+
+class FITSImageBuffer(FITSImageData):
+    pass
 
 def sanitize_fits_unit(unit):
     if unit == "Mpc":
@@ -309,11 +417,9 @@
         unit = "AU"
     return unit
 
-def construct_image(data_source, center=None, width=None, image_res=None):
-    ds = data_source.ds
-    axis = data_source.axis
-    if center is None or width is None:
-        center = ds.domain_center[axis_wcs[axis]]
+axis_wcs = [[1,2],[0,2],[0,1]]
+
+def construct_image(ds, axis, data_source, center, width=None, image_res=None):
     if width is None:
         width = ds.domain_width[axis_wcs[axis]]
         unit = ds.get_smallest_appropriate_unit(width[0])
@@ -323,28 +429,28 @@
         width = ds.coordinates.sanitize_width(axis, width, None)
         unit = str(width[0].units)
     if image_res is None:
-        dd = ds.all_data()
-        dx, dy = [dd.quantities.extrema("d%s" % "xyz"[idx])[0]
-                  for idx in axis_wcs[axis]]
-        nx = int((width[0]/dx).in_units("dimensionless"))
-        ny = int((width[1]/dy).in_units("dimensionless"))
+        ddims = ds.domain_dimensions*ds.refine_by**ds.index.max_level
+        if iterable(axis):
+            nx = ddims.max()
+            ny = ddims.max()
+        else:
+            nx, ny = [ddims[idx] for idx in axis_wcs[axis]]
     else:
         if iterable(image_res):
             nx, ny = image_res
         else:
             nx, ny = image_res, image_res
-        dx, dy = width[0]/nx, width[1]/ny
+    dx, dy = width[0]/nx, width[1]/ny
     crpix = [0.5*(nx+1), 0.5*(ny+1)]
-    if hasattr(ds, "wcs"):
+    if hasattr(ds, "wcs") and not iterable(axis):
         # This is a FITS dataset, so we use it to construct the WCS
         cunit = [str(ds.wcs.wcs.cunit[idx]) for idx in axis_wcs[axis]]
         ctype = [ds.wcs.wcs.ctype[idx] for idx in axis_wcs[axis]]
         cdelt = [ds.wcs.wcs.cdelt[idx] for idx in axis_wcs[axis]]
         ctr_pix = center.in_units("code_length")[:ds.dimensionality].v
-        crval = ds.wcs.wcs_pix2world(ctr_pix.reshape(1,ds.dimensionality))[0]
+        crval = ds.wcs.wcs_pix2world(ctr_pix.reshape(1, ds.dimensionality))[0]
         crval = [crval[idx] for idx in axis_wcs[axis]]
     else:
-        # This is some other kind of dataset                                                                      
         if unit == "unitary":
             unit = ds.get_smallest_appropriate_unit(ds.domain_width.max())
         elif unit == "code_length":
@@ -353,8 +459,17 @@
         cunit = [unit]*2
         ctype = ["LINEAR"]*2
         cdelt = [dx.in_units(unit)]*2
-        crval = [center[idx].in_units(unit) for idx in axis_wcs[axis]]
-    frb = data_source.to_frb(width[0], (nx,ny), center=center, height=width[1])
+        if iterable(axis):
+            crval = center.in_units(unit)
+        else:
+            crval = [center[idx].in_units(unit) for idx in axis_wcs[axis]]
+    if hasattr(data_source, 'to_frb'):
+        if iterable(axis):
+            frb = data_source.to_frb(width[0], (nx, ny), height=width[1])
+        else:
+            frb = data_source.to_frb(width[0], (nx, ny), center=center, height=width[1])
+    else:
+        frb = None
     w = pywcs.WCS(naxis=2)
     w.wcs.crpix = crpix
     w.wcs.cdelt = cdelt
@@ -363,14 +478,42 @@
     w.wcs.ctype = ctype
     return w, frb
 
-class FITSSlice(FITSImageBuffer):
+def assert_same_wcs(wcs1, wcs2):
+    from numpy.testing import assert_allclose
+    assert wcs1.naxis == wcs2.naxis
+    for i in range(wcs1.naxis):
+        assert wcs1.wcs.cunit[i] == wcs2.wcs.cunit[i]
+        assert wcs1.wcs.ctype[i] == wcs2.wcs.ctype[i]
+    assert_allclose(wcs1.wcs.crpix, wcs2.wcs.crpix)
+    assert_allclose(wcs1.wcs.cdelt, wcs2.wcs.cdelt)
+    assert_allclose(wcs1.wcs.crval, wcs2.wcs.crval)
+    crota1 = getattr(wcs1.wcs, "crota", None)
+    crota2 = getattr(wcs2.wcs, "crota", None)
+    if crota1 is None or crota2 is None:
+        assert crota1 == crota2
+    else:
+        assert_allclose(wcs1.wcs.crota, wcs2.wcs.crota)
+    cd1 = getattr(wcs1.wcs, "cd", None)
+    cd2 = getattr(wcs2.wcs, "cd", None)
+    if cd1 is None or cd2 is None:
+        assert cd1 == cd2
+    else:
+        assert_allclose(wcs1.wcs.cd, wcs2.wcs.cd)
+    pc1 = getattr(wcs1.wcs, "pc", None)
+    pc2 = getattr(wcs2.wcs, "pc", None)
+    if pc1 is None or pc2 is None:
+        assert pc1 == pc2
+    else:
+        assert_allclose(wcs1.wcs.pc, wcs2.wcs.pc)
+
+class FITSSlice(FITSImageData):
     r"""
-    Generate a FITSImageBuffer of an on-axis slice.
+    Generate a FITSImageData of an on-axis slice.
 
     Parameters
     ----------
-    ds : FITSDataset
-        The FITS dataset object.
+    ds : :class:`yt.data_objects.api.Dataset`
+        The dataset object.
     axis : character or integer
         The axis of the slice. One of "x","y","z", or 0,1,2.
     fields : string or list of strings
@@ -414,20 +557,18 @@
         axis = fix_axis(axis, ds)
         center, dcenter = ds.coordinates.sanitize_center(center, axis)
         slc = ds.slice(axis, center[axis], **kwargs)
-        w, frb = construct_image(slc, center=dcenter, width=width,
-                                 image_res=image_res)
+        w, frb = construct_image(ds, axis, slc, dcenter, width=width, image_res=image_res)
         super(FITSSlice, self).__init__(frb, fields=fields, wcs=w)
-        for i, field in enumerate(fields):
-            self[i].header["bunit"] = str(frb[field].units)
 
-class FITSProjection(FITSImageBuffer):
+
+class FITSProjection(FITSImageData):
     r"""
-    Generate a FITSImageBuffer of an on-axis projection.
+    Generate a FITSImageData of an on-axis projection.
 
     Parameters
     ----------
-    ds : FITSDataset
-        The FITS dataset object.
+    ds : :class:`yt.data_objects.api.Dataset`
+        The dataset object.
     axis : character or integer
         The axis along which to project. One of "x","y","z", or 0,1,2.
     fields : string or list of strings
@@ -468,14 +609,161 @@
         Specify the resolution of the resulting image. If not provided, it will be
         determined based on the minimum cell size of the dataset.
     """
-    def __init__(self, ds, axis, fields, center="c", width=None, 
+    def __init__(self, ds, axis, fields, center="c", width=None,
                  weight_field=None, image_res=None, **kwargs):
         fields = ensure_list(fields)
         axis = fix_axis(axis, ds)
         center, dcenter = ds.coordinates.sanitize_center(center, axis)
         prj = ds.proj(fields[0], axis, weight_field=weight_field, **kwargs)
-        w, frb = construct_image(prj, center=dcenter, width=width,
-                                 image_res=image_res)
+        w, frb = construct_image(ds, axis, prj, dcenter, width=width, image_res=image_res)
         super(FITSProjection, self).__init__(frb, fields=fields, wcs=w)
-        for i, field in enumerate(fields):
-            self[i].header["bunit"] = str(frb[field].units)
+
+class FITSOffAxisSlice(FITSImageData):
+    r"""
+    Generate a FITSImageData of an off-axis slice.
+
+    Parameters
+    ----------
+    ds : :class:`yt.data_objects.api.Dataset`
+        The dataset object.
+    normal : a sequence of floats
+        The vector normal to the projection plane.
+    fields : string or list of strings
+        The fields to slice
+    center : A sequence of floats, a string, or a tuple.
+        The coordinate of the center of the image. If set to 'c', 'center' or
+        left blank, the plot is centered on the middle of the domain. If set to
+        'max' or 'm', the center will be located at the maximum of the
+        ('gas', 'density') field. Centering on the max or min of a specific
+        field is supported by providing a tuple such as ("min","temperature") or
+        ("max","dark_matter_density"). Units can be specified by passing in *center*
+        as a tuple containing a coordinate and string unit name or by passing
+        in a YTArray. If a list or unitless array is supplied, code units are
+        assumed.
+    width : tuple or a float.
+        Width can have four different formats to support windows with variable
+        x and y widths.  They are:
+
+        ==================================     =======================
+        format                                 example
+        ==================================     =======================
+        (float, string)                        (10,'kpc')
+        ((float, string), (float, string))     ((10,'kpc'),(15,'kpc'))
+        float                                  0.2
+        (float, float)                         (0.2, 0.3)
+        ==================================     =======================
+
+        For example, (10, 'kpc') requests a plot window that is 10 kiloparsecs
+        wide in the x and y directions, ((10,'kpc'),(15,'kpc')) requests a
+        window that is 10 kiloparsecs wide along the x axis and 15
+        kiloparsecs wide along the y axis.  In the other two examples, code
+        units are assumed, for example (0.2, 0.3) requests a plot that has an
+        x width of 0.2 and a y width of 0.3 in code units.  If units are
+        provided the resulting plot axis labels will use the supplied units.
+    image_res : an int or 2-tuple of ints
+        Specify the resolution of the resulting image.
+    north_vector : a sequence of floats
+        A vector defining the 'up' direction in the plot.  This
+        option sets the orientation of the slicing plane.  If not
+        set, an arbitrary grid-aligned north-vector is chosen.
+    """
+    def __init__(self, ds, normal, fields, center='c', width=None, image_res=512,
+                 north_vector=None):
+        fields = ensure_list(fields)
+        center, dcenter = ds.coordinates.sanitize_center(center, 4)
+        cut = ds.cutting(normal, center, north_vector=north_vector)
+        center = ds.arr([0.0] * 2, 'code_length')
+        w, frb = construct_image(ds, normal, cut, center, width=width, image_res=image_res)
+        super(FITSOffAxisSlice, self).__init__(frb, fields=fields, wcs=w)
+
+
+class FITSOffAxisProjection(FITSImageData):
+    r"""
+    Generate a FITSImageData of an off-axis projection.
+
+    Parameters
+    ----------
+    ds : :class:`yt.data_objects.api.Dataset`
+        This is the dataset object corresponding to the
+        simulation output to be plotted.
+    normal : a sequence of floats
+        The vector normal to the projection plane.
+    fields : string, list of strings
+        The name of the field(s) to be plotted.
+    center : A sequence of floats, a string, or a tuple.
+         The coordinate of the center of the image. If set to 'c', 'center' or
+         left blank, the plot is centered on the middle of the domain. If set to
+         'max' or 'm', the center will be located at the maximum of the
+         ('gas', 'density') field. Centering on the max or min of a specific
+         field is supported by providing a tuple such as ("min","temperature") or
+         ("max","dark_matter_density"). Units can be specified by passing in *center*
+         as a tuple containing a coordinate and string unit name or by passing
+         in a YTArray. If a list or unitless array is supplied, code units are
+         assumed.
+    width : tuple or a float.
+         Width can have four different formats to support windows with variable
+         x and y widths.  They are:
+
+         ==================================     =======================
+         format                                 example
+         ==================================     =======================
+         (float, string)                        (10,'kpc')
+         ((float, string), (float, string))     ((10,'kpc'),(15,'kpc'))
+         float                                  0.2
+         (float, float)                         (0.2, 0.3)
+         ==================================     =======================
+
+         For example, (10, 'kpc') requests a plot window that is 10 kiloparsecs
+         wide in the x and y directions, ((10,'kpc'),(15,'kpc')) requests a
+         window that is 10 kiloparsecs wide along the x axis and 15
+         kiloparsecs wide along the y axis.  In the other two examples, code
+         units are assumed, for example (0.2, 0.3) requests a plot that has an
+         x width of 0.2 and a y width of 0.3 in code units.  If units are
+         provided the resulting plot axis labels will use the supplied units.
+    depth : A tuple or a float
+         A tuple containing the depth to project through and the string
+         key of the unit: (width, 'unit').  If set to a float, code units
+         are assumed
+    weight_field : string
+         The name of the weighting field.  Set to None for no weight.
+    image_res : an int or 2-tuple of ints
+        Specify the resolution of the resulting image. 
+    depth_res : an int 
+        Specify the resolution of the depth of the projection.
+    north_vector : a sequence of floats
+         A vector defining the 'up' direction in the plot.  This
+         option sets the orientation of the slicing plane.  If not
+         set, an arbitrary grid-aligned north-vector is chosen.
+    method : string
+         The method of projection.  Valid methods are:
+
+         "integrate" with no weight_field specified : integrate the requested
+         field along the line of sight.
+
+         "integrate" with a weight_field specified : weight the requested
+         field by the weighting field and integrate along the line of sight.
+
+         "sum" : This method is the same as integrate, except that it does not
+         multiply by a path length when performing the integration, and is
+         just a straight summation of the field along the given axis. WARNING:
+         This should only be used for uniform resolution grid datasets, as other
+         datasets may result in unphysical images.
+    """
+    def __init__(self, ds, normal, fields, center='c', width=(1.0, 'unitary'),
+                 weight_field=None, image_res=512, depth_res=256,
+                 north_vector=None, depth=(1.0,"unitary"), no_ghost=False, method='integrate'):
+        fields = ensure_list(fields)
+        center, dcenter = ds.coordinates.sanitize_center(center, 4)
+        buf = {}
+        width = ds.coordinates.sanitize_width(normal, width, depth)
+        wd = tuple(el.in_units('code_length').v for el in width)
+        if not iterable(image_res):
+            image_res = (image_res, image_res)
+        res = (image_res[0], image_res[1], depth_res)
+        for field in fields:
+            buf[field] = off_axis_projection(ds, center, normal, wd, res, field,
+                                             no_ghost=no_ghost, north_vector=north_vector,
+                                             method=method, weight=weight_field).swapaxes(0, 1)
+        center = ds.arr([0.0] * 2, 'code_length')
+        w, not_an_frb = construct_image(ds, normal, buf, center, width=width, image_res=image_res)
+        super(FITSOffAxisProjection, self).__init__(buf, fields=fields, wcs=w)

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/utilities/tests/test_fits_image.py
--- /dev/null
+++ b/yt/utilities/tests/test_fits_image.py
@@ -0,0 +1,128 @@
+"""
+Unit test FITS image creation in yt.
+
+
+
+"""
+
+#-----------------------------------------------------------------------------
+# Copyright (c) 2013, yt Development Team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file COPYING.txt, distributed with this software.
+#-----------------------------------------------------------------------------
+
+import tempfile
+import os
+import numpy as np
+import shutil
+from yt.testing import fake_random_ds
+from yt.convenience import load
+from numpy.testing import \
+    assert_equal
+from yt.utilities.fits_image import \
+    FITSImageData, FITSProjection, \
+    FITSSlice, FITSOffAxisSlice, \
+    FITSOffAxisProjection, \
+    assert_same_wcs
+from yt.visualization.volume_rendering.camera import \
+    off_axis_projection
+
+def test_fits_image():
+    tmpdir = tempfile.mkdtemp()
+    curdir = os.getcwd()
+    os.chdir(tmpdir)
+
+    fields = ("density", "temperature")
+    units = ('g/cm**3', 'K',)
+    ds = fake_random_ds(64, fields=fields, units=units, nprocs=16,
+                        length_unit=100.0)
+
+    prj = ds.proj("density", 2)
+    prj_frb = prj.to_frb((0.5, "unitary"), 128)
+
+    fid1 = FITSImageData(prj_frb, fields=["density","temperature"], units="cm")
+    fits_prj = FITSProjection(ds, "z", ["density","temperature"], image_res=128,
+                              width=(0.5,"unitary"))
+
+    yield assert_equal, fid1.get_data("density"), fits_prj.get_data("density")
+    yield assert_equal, fid1.get_data("temperature"), fits_prj.get_data("temperature")
+
+    fid1.writeto("fid1.fits", clobber=True)
+    new_fid1 = FITSImageData.from_file("fid1.fits")
+
+    yield assert_equal, fid1.get_data("density"), new_fid1.get_data("density")
+    yield assert_equal, fid1.get_data("temperature"), new_fid1.get_data("temperature")
+
+    ds2 = load("fid1.fits")
+    ds2.index
+
+    assert ("fits","density") in ds2.field_list
+    assert ("fits","temperature") in ds2.field_list
+
+    dw_cm = ds2.domain_width.in_units("cm")
+
+    assert dw_cm[0].v == 50.
+    assert dw_cm[1].v == 50.
+
+    slc = ds.slice(2, 0.5)
+    slc_frb = slc.to_frb((0.5, "unitary"), 128)
+
+    fid2 = FITSImageData(slc_frb, fields=["density","temperature"], units="cm")
+    fits_slc = FITSSlice(ds, "z", ["density","temperature"], image_res=128,
+                         width=(0.5,"unitary"))
+
+    yield assert_equal, fid2.get_data("density"), fits_slc.get_data("density")
+    yield assert_equal, fid2.get_data("temperature"), fits_slc.get_data("temperature")
+
+    dens_img = fid2.pop("density")
+    temp_img = fid2.pop("temperature")
+
+    # This already has some assertions in it, so we don't need to do anything
+    # with it other can just make one
+    fid_comb = FITSImageData.from_images([dens_img, temp_img])
+
+    cut = ds.cutting([0.1, 0.2, -0.9], [0.5, 0.42, 0.6])
+    cut_frb = cut.to_frb((0.5, "unitary"), 128)
+
+    fid3 = FITSImageData(cut_frb, fields=["density","temperature"], units="cm")
+    fits_cut = FITSOffAxisSlice(ds, [0.1, 0.2, -0.9], ["density","temperature"], 
+                                image_res=128, center=[0.5, 0.42, 0.6],
+                                width=(0.5,"unitary"))
+
+    yield assert_equal, fid3.get_data("density"), fits_cut.get_data("density")
+    yield assert_equal, fid3.get_data("temperature"), fits_cut.get_data("temperature")
+
+    fid3.create_sky_wcs([30.,45.], (1.0,"arcsec/kpc"))
+    fid3.writeto("fid3.fits", clobber=True)
+    new_fid3 = FITSImageData.from_file("fid3.fits")
+    assert_same_wcs(fid3.wcs, new_fid3.wcs)
+    assert new_fid3.wcs.wcs.cunit[0] == "deg"
+    assert new_fid3.wcs.wcs.cunit[1] == "deg"
+    assert new_fid3.wcs.wcs.ctype[0] == "RA---TAN"
+    assert new_fid3.wcs.wcs.ctype[1] == "DEC--TAN"
+
+    buf = off_axis_projection(ds, ds.domain_center, [0.1, 0.2, -0.9], 
+                              0.5, 128, "density").swapaxes(0, 1)
+    fid4 = FITSImageData(buf, fields="density", width=100.0)
+    fits_oap = FITSOffAxisProjection(ds, [0.1, 0.2, -0.9], "density", 
+                                     width=(0.5,"unitary"), image_res=128, 
+                                     depth_res=128, depth=(0.5,"unitary"))
+
+    yield assert_equal, fid4.get_data("density"), fits_oap.get_data("density")
+
+    cvg = ds.covering_grid(ds.index.max_level, [0.25,0.25,0.25], 
+                           [32, 32, 32], fields=["density","temperature"])
+    fid5 = FITSImageData(cvg, fields=["density","temperature"])
+    assert fid5.dimensionality == 3
+
+    fid5.update_header("density", "time", 0.1)
+    fid5.update_header("all", "units", "cgs")
+    
+    assert fid5["density"].header["time"] == 0.1
+    assert fid5["temperature"].header["units"] == "cgs"
+    assert fid5["density"].header["units"] == "cgs"
+    
+    os.chdir(curdir)
+    shutil.rmtree(tmpdir)

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/visualization/fixed_resolution.py
--- a/yt/visualization/fixed_resolution.py
+++ b/yt/visualization/fixed_resolution.py
@@ -327,11 +327,11 @@
             the length units that the coordinates are written in, default 'cm'.
         """
 
-        from yt.utilities.fits_image import FITSImageBuffer
+        from yt.utilities.fits_image import FITSImageData
 
         if fields is None: fields = list(self.data.keys())
 
-        fib = FITSImageBuffer(self, fields=fields, units=units)
+        fib = FITSImageData(self, fields=fields, units=units)
         if other_keys is not None:
             for k,v in other_keys.items():
                 fib.update_all_headers(k,v)
@@ -470,7 +470,7 @@
 
     def __getitem__(self, item):
         if item in self.data: return self.data[item]
-        mylog.info("Making a fixed resolutuion buffer of (%s) %d by %d" % \
+        mylog.info("Making a fixed resolution buffer of (%s) %d by %d" % \
             (item, self.buff_size[0], self.buff_size[1]))
         dd = self.data_source
         width = self.ds.arr((self.bounds[1] - self.bounds[0],

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/visualization/volume_rendering/camera.py
--- a/yt/visualization/volume_rendering/camera.py
+++ b/yt/visualization/volume_rendering/camera.py
@@ -2252,7 +2252,6 @@
             def temp_weightfield(a, b):
                 tr = b[f].astype("float64") * b[w]
                 return b.apply_units(tr, a.units)
-                return tr
             return temp_weightfield
         ds.field_info.add_field(weightfield,
             function=_make_wf(field, weight))

diff -r 73ca90e953997cb93a5b04ff33090839f55e2feb -r e4bc6b4f239bd0a557e3819586330a75028f4c4f yt/visualization/volume_rendering/image_handling.py
--- a/yt/visualization/volume_rendering/image_handling.py
+++ b/yt/visualization/volume_rendering/image_handling.py
@@ -33,14 +33,14 @@
         f.create_dataset("A", data=image[:,:,3])
         f.close()
     if fits:
-        from yt.utilities.fits_image import FITSImageBuffer
+        from yt.utilities.fits_image import FITSImageData
         data = {}
         data["r"] = image[:,:,0]
         data["g"] = image[:,:,1]
         data["b"] = image[:,:,2]
         data["a"] = image[:,:,3]
         nx, ny = data["r"].shape
-        fib = FITSImageBuffer(data)
+        fib = FITSImageData(data)
         fib.writeto('%s.fits'%fn,clobber=True)
 
 def import_rgba(name, h5=True):

Repository URL: https://bitbucket.org/yt_analysis/yt/

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