[yt-users] Error in visualization with new derived field

[Nathan Goldbaum]

Hi Junhwan

In fact, in general you'll get back a 1D array.  These are the collapsed values for the data in a single grid (i.e. flattened from 3D to 1D).

Since your field does not explicitly depend on the 3D nature of the grid, this is an easy fix:

def _DensityCeiling(field, data):
    Ceiling = 1e-22
    wh = np.where(data["Density"] < Ceiling)
    DensityCeiling = data["Density"]
    DensityCeiling[wh] = Ceiling
    return DensityCeiling

Here np is how I've imported numpy locally.  There may be an even cleverer way of doing the array manipulation that someone else on the list may know of off-hand.

Cheers,

Nathan

On Oct 4, 2012, at 2:00 PM, Jun-Hwan Choi wrote:

> Hi yt-users,
> 
> I try to make a density projection of my simulation.
> I would like to make a small modification that if the cell density higher than a given density ceiling the density value becomes the density ceiling.
> And, I made a following script:
> ############################################
> from yt.mods import *
> import matplotlib.pylab as pylab
> 
> def _DensityCeiling(field, data):
>     Ceiling = 1e-22
>     nx, ny, nz = data["Density"].shape
>     DensityCeiling =  na.zeros(data["Density"].shape, dtype='float64')
>     DensityCeiling = data["Density"]
>     for ix, in range(0,nx):
>         for iy, in range(0,ny):
>             for iz, in range(0,nz):
>                 if(data["DensityCeiling"][ix,iy,iz]  > Ceiling):
>                     DensityCeiling[ix,iy,iz] = Ceiling
>     return DensityCeiling
> add_field("DensityCeiling", function=_DensityCeiling, units=r"\rm{g}/\rm{cm^3}")
> 
> 
> # load up a dataset
> pf = load("DD0000/DD0000")
> all_center = [0.5, 0.5, 0.5]
> 
> pc = PlotCollection(pf,center=all_center)
> pc.add_slice("DensityCeiling", 0)
> pc.add_slice("DensityCeiling", 2)
> pc.add_projection("DensityCeiling", 0)
> pc.add_projection("DensityCeiling", 2)
> 
> pc.set_width(6, 'kpc')
> pc.save("cen_t%04.1f_L6K" % pf.current_time)
> pc.set_width(1, 'kpc')
> pc.save("cen_t%04.1f_L1K" % pf.current_time)
> #######################################################
> 
> And then, I got a following error.
> File "DenViz.py", line 6, in _DensityCeiling
>  nx, ny, nz = data["Density"].shape
> ValueError: need more than 1 value to unpack
> 
> It turns out that the data["Density"] is not always 3d array but sometimes become 1d array.
> Is there any way to fix the derived field to avoid this problem?
> 
> Thank you in advance,
> Junhwan
> 
> 
>  -- 
> --------------------------------------------------------------
> Jun-Hwan Choi, Ph.D.
> Department of Physics and Astronomy, University of Kentucky
> Tel: (859) 897-6737        Fax: (859) 323-2846
> Email: jhchoi at pa.uky.edu   URL: http://www.pa.uky.edu/~jhchoi
> --------------------------------------------------------------
> _______________________________________________
> yt-users mailing list
> yt-users at lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org

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