[yt-users] Projection

[Nathan Goldbaum]

Ah, so this isn't actually a bug. There's even a comment in the code
indicating that this is the intended behavior:

https://github.com/yt-project/yt/blob/master/yt/data_objects/construction_data_containers.py#L373

So the choices about what to do here are, in my opinion:

* Change this behavior to fill the array with zeros instead of NaNs
* Improve the documentation to make this choice clearer

I'm not sure offhand what is the best approach, especially given that
changing this behavior would be a backward compatibility break.

For the original question: your data aren't all NaNs I suspect. E.g. take a
look at this example script:

import yt
import numpy as np
ds = yt.load('IsolatedGalaxy/galaxy0030/galaxy0030')
disk = ds.disk('c', [0, 0, 1], (1000, 'pc'), (100, 'pc'))
proj = ds.proj('density', axis='z', weight_field='density',
data_source=disk,
               method='integrate')
dens_proj = proj['density']
print(dens_proj[np.isfinite(dens_proj)])
print(np.nanmax(dens_proj))
print(np.nanmin(dens_proj))

Which prints out values in regions where the projection isn't filled with
NaNs.


On Tue, Nov 14, 2017 at 12:45 PM, José Mauricio Utreras <
jutreras at ug.uchile.cl> wrote:

> Hi everyone,
>
> I got the same result using the IsolatedGalaxy dataset
>
> ds=yt.load('IsolatedGalaxy/galaxy0030/galaxy0030')
> disk = ds.disk('c',[0,0,1],(1000,'pc'),(100,'pc'))
> proj=ds.proj('density',axis='z',weight_field='density',
> data_source=disk,method='integrate')
> proj['density']
> >>> YTArray([ nan,  nan,  nan, ...,  nan,  nan,  nan]) g/cm**3
>
> 2017-11-14 15:38 GMT-03:00, Nathan Goldbaum <nathan12343 at gmail.com>:
> > Can I get one of you to open an issue?
> >
> > https://github.com/yt-project/yt/issues/new
> >
> > If you can, please include a script to reproduce the problem, making use
> of
> > one of the public datasets on yt-project.org/data.
> >
> > -Nathan
> >
> > On Tue, Nov 14, 2017 at 12:34 PM, Andrew James Emerick
> > <aje2123 at columbia.edu
> >> wrote:
> >
> >> Hello Matias and Nathan,
> >>
> >> I was able to reproduce this error on my own Enzo data set(s) using
> >> similar code. I did a little more playing around and it looks like it
> >> only
> >> breaks when having a weight_field. weight_field = None seems to be O.K.
> .
> >> It also occurs for the "region" objects, in addition to the disk.
> >> Interestingly, as Matias pointed out, doing something like this works:
> >>
> >> region = ds.region([0.5,0.5,0.5], [0.0, 0.0, 0.0], [1.0, 1.0, 1.0])
> >> proj=ds.proj('density',axis='z',weight_field='density',data_
> >> source=region,method='integrate')
> >>
> >> but this does not:
> >>
> >> region = ds.region([0.5,0.5,0.5], [0.1,0.1,0.1], [0.9,0.9,0.9] )
> >> proj =ds.proj('density',axis='z',weight_field='density',data_
> >> source=region,method='integrate')
> >>
> >> In short, this indeed appears to be a bug, and possibly not specific to
> a
> >> single dataset.
> >>
> >>
> >>
> >>
> >> Andrew
> >>
> >>
> >> On Tue, Nov 14, 2017 at 12:40 PM, Nathan Goldbaum <
> nathan12343 at gmail.com>
> >> wrote:
> >>
> >>> This sounds like a bug. I don't think you should ever get back NaNs
> from
> >>> a projection operation.
> >>>
> >>> Is there any chance you can share the dataset that's triggering this
> >>> behavior?
> >>>
> >>> On Tue, Nov 14, 2017 at 11:34 AM, Matias Enrique Suazo Campos <
> >>> matias.suazo at ug.uchile.cl> wrote:
> >>>
> >>>> Dear YT users,
> >>>>
> >>>> I'm trying to make a density projection, in the following lines I show
> >>>> you the lines that I have.
> >>>>
> >>>> #Ramses output
> >>>> ds = yt.load(path+"output_%05d"%snap+"/info_%05d.txt" %snap)
> >>>> disk = ds.disk('max',[0,0,1],(20,'pc'),(5,'pc'))
> >>>> proj=ds.proj('density',axis='z',weight_field='density',data_
> >>>> source=disk,method='integrate')
> >>>>
> >>>> However when I print proj["density"] I get a list of nan, however when
> >>>> I
> >>>> use the whole domain as my data_source I get reasonable numbers.
> >>>>
> >>>> Thanks,
> >>>> Matías Suazo
> >>>> MSc student at Universidad de Chile
> >>>>
> >>>> _______________________________________________
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> >>>>
> >>>>
> >>>
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> >>
> >>
> >> --
> >> NSF Graduate Fellow
> >> Columbia University
> >> Department of Astronomy
> >>
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