[yt-users] Creating image from FITS data

tazkera haque h.tazkera at gmail.com
Sun Sep 10 17:46:25 PDT 2017


Hi John,

Thanks so much for all the help. I just need one more clarification from
you. I needed to identify values greater than 4.5 and draw a circle around
them. I used the masking function in yt to figure out the array which
contains those certain values. But Can you please show me how do I draw
circles around them in the same 2d plot?








*hot = dd["image_0"].in_units('dimensionless') > 4.5print('Temperature of
all data: dd["image_0"] = \n%s' % dd["image_0"])print("Boolean Mask: hot =
\n%s" % hot)print('Temperature of "hot" data: dd["image_0"][hot] = \n%s'
%      dd['image_0'][hot])q = dd['image_0'][hot]print q*
Thanks a lot

Tazkera

On Sun, Sep 10, 2017 at 12:22 PM, John ZuHone <jzuhone at gmail.com> wrote:

> Hi Tazkera,
>
> The issue here is that sp[“image_0”] is a 1-D array of the points in the
> sphere. If you want to make plots using yt, I would suggest checking out
> the plotting documentation:
>
> http://yt-project.org/doc/visualizing/plots.html
>
> Specifically, since you have a 2D fits file, it’d probably be simplest to
> use plot_2d:
>
> http://yt-project.org/doc/visualizing/plots.html#plots-of-2d-datasets
>
> If you want to cut out the data that isn’t in your sphere object, you can
> try passing the sphere object in as the data_source argument to plot_2d:
>
> p = yt.plot_2d(ds, “image_0”, data_source=sp)
> p.save()
>
> That should give you a head start.
>
> Best,
>
> John
>
> On Sep 9, 2017, at 8:02 PM, tazkera haque <h.tazkera at gmail.com> wrote:
>
> Hi People,
>
> I am trying to play around with FITS file format. I want to create an
> image from this file which will include data from center to 20 arc minutes.
> each pixel is 3x3 arc sec.
>
> *import yt*
> *ds = yt.load("signal_wfilt_sn.fits")*
> *ds.print_stats()*
>
> *ds.field_list*
>
> *ds.domain_width*
>
> *ds.derived_field_list*
> *dd = ds.all_data()*
> *dd*
>
> *sp = ds.sphere(ds.domain_center, (400, 'code_length'))  # create sphere
> of 20 arcminutes with 3x3 pixel size*
>
> *sp[("fits", "image_0")]
>        # check array of data within the sphere*
> *#plot 1D histogram of data over pixel*
> *pplot = yt.ProfilePlot(sp, "image_0", ["pixel"], weight_field=None,
> n_bins=1024, *
> *plot_spec=dict(color='red', linestyle="--"), y_log={'pixel':False})*
> *pplot.show()*
> *# convert data to numpy array*
> *import numpy as np*
> *image = np.array(sp['image_0'])*
>
> *# create image?*
> *imgplot = plt.imshow(image)*
>
> *imgplot*
> *plt.show()*
> *image*
>
> *The code is failing at this point with error:*
>
> ---------------------------------------------------------------------------TypeError                                 Traceback (most recent call last)<ipython-input-21-6a83e68fbbf2> in <module>()----> 1 imgplot = plt.imshow(image)      2       3 imgplot      4 plt.show()
> /home/trina/anaconda2/lib/python2.7/site-packages/matplotlib/pyplot.pyc in imshow(X, cmap, norm, aspect, interpolation, alpha, vmin, vmax, origin, extent, shape, filternorm, filterrad, imlim, resample, url, hold, data, **kwargs)   3155                         filternorm=filternorm, filterrad=filterrad,   3156                         imlim=imlim, resample=resample, url=url, data=data,-> 3157                         **kwargs)   3158     finally:   3159         ax._hold = washold
> /home/trina/anaconda2/lib/python2.7/site-packages/matplotlib/__init__.pyc in inner(ax, *args, **kwargs)   1896                     warnings.warn(msg % (label_namer, func.__name__),   1897                                   RuntimeWarning, stacklevel=2)-> 1898             return func(ax, *args, **kwargs)   1899         pre_doc = inner.__doc__   1900         if pre_doc is None:
> /home/trina/anaconda2/lib/python2.7/site-packages/matplotlib/axes/_axes.pyc in imshow(self, X, cmap, norm, aspect, interpolation, alpha, vmin, vmax, origin, extent, shape, filternorm, filterrad, imlim, resample, url, **kwargs)   5122                               resample=resample, **kwargs)   5123 -> 5124         im.set_data(X)   5125         im.set_alpha(alpha)   5126         if im.get_clip_path() is None:
> /home/trina/anaconda2/lib/python2.7/site-packages/matplotlib/image.pyc in set_data(self, A)    598         if (self._A.ndim not in (2, 3) or    599                 (self._A.ndim == 3 and self._A.shape[-1] not in (3, 4))):--> 600             raise TypeError("Invalid dimensions for image data")    601     602         self._imcache = None
> TypeError: Invalid dimensions for image data
>
>
> I am completely new to image processing, so I am interested to know how
> you create image for this type of data in yt. Your help is very
> appreciated. I also provided a link to the dataset:
>
> https://www.dropbox.com/s/bftuihqcoun8tny/signal_wfilt_sn.fits?dl=0
> Thanks a lot
> Tazkera haque
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