[yt-users] cut_region bafflement

[Nathan Goldbaum]

Hi Stephanie,

I'm not sure off-hand why this is happening.

It may help one of us to be able to reproduce and understand what you're
seeing if you can phrase your question in the form of an example that one
of can run locally. This would make use of one of the test datasets on
yt-project.org/data, and a full script that we can run locally pasted to
paste.yt-project.org/data

Finally, just to clarify, the confusion is that the volumes of P3 and P4
are *bigger* than P2 and identical?

It might be the case that the derived quantity infrastructure is somehow
selecting the data as if it were selecting from ds.all_data() instead of
your disk selector.  Can you try computing what the total volume of cells
in a data object constructed by applying cut_regions on ds.all_data()
instead of ds.disk()?

-Nathan

On Wed, Oct 7, 2015 at 5:21 PM, Stephanie Tonnesen <stonnes at gmail.com>
wrote:

> Dear yt-users,
>
> I am running
>
> Version = 3.2-dev
> Changeset = dc2467c4eae7 (yt) tip
>
> I have been fiddling around with cut_region in a disk region and have
> gotten really confused.  I was initially trying to see whether defining a
> disk region such that the cylinder height was on the x-axis changed how I
> need to make a cut in the cylinder height.  Anyway, as I was fiddling with
> these cuts I found that if I made a "spatial" cut (rather than a different
> variable cut) I was getting different volumes.  Let me show you:
>
> small bit of background:  the whole box is 130 kpc across, so 0.5 0.5 0.5
> is 65 65 65 kpc.  Also, I am cutting and pasting bits here so the
> indentation is off.
>
> ds =
> yt.load("/data/stonnes/dwarf_nowind_lowmassgal_bigtracer/DD"+loop[i]+"/DD44sMBhn25now"+loop[i])
>
> r2 = ds.disk([0.5,0.5,0.5],[-1,0,0],(4,"kpc"),(2,"kpc"))
>     r2c = r2.cut_region(["obj['Metal_Density']/obj['density'] > 0.33"])
>
>     r3 = ds.disk([0.5,0.5,0.5],[-1,0,0],(4,"kpc"),(2,"kpc"))
>     r3r = r3.cut_region(["(obj['x'].in_units('kpc') > 63.0)"])
>     r3r = r3r.cut_region(["(obj['x'].in_units('kpc') < 67.0)"])
>     r3c = r3r.cut_region(["obj['Metal_Density']/obj['density'] > 0.33"])
>
>     r4 = ds.disk([0.5,0.5,0.5],[-1,0,0],(4,"kpc"),(2,"kpc"))
>     r4r = r4.cut_region(["(obj['x'].in_units('kpc') > 61.)"])
>     r4c = r4r.cut_region(["obj['Metal_Density']/obj['density'] > 0.33"])
>
>  P2 =
> np.append(P2,r2c.quantities.total_quantity([("index","cell_volume")]))
>  P3 =
> np.append(P3,r3c.quantities.total_quantity([("index","cell_volume")]))
>  P4 =
> np.append(P4,r4c.quantities.total_quantity([("index","cell_volume")]))
>
> P2 volume is 9.346e-5 : within 2% of my calculation for the volume I
> should be getting
> P3 volume is 7.4768e-4
> P4 volume is 7.4768e-4
>
> When I print out the x- y- and z- maxes and mins, they are the same for
> each of the selected regions.
> (By doing this:
> m2 = np.append(m2,r2c.quantities.extrema([("index","z")])[0])
> rho2 = np.append(rho2,r2c.quantities.extrema([("index","z")])[1])
>
> )
>
> Can anyone help me figure out/tell me what is going on here?
>
> Thanks!
> Stephanie
>
> --
> Dr. Stephanie Tonnesen
> Alvin E. Nashman Postdoctoral Fellow
> Carnegie Observatories, Pasadena, CA
> stonnes at gmail.com
>
> _______________________________________________
> yt-users mailing list
> yt-users at lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.spacepope.org/pipermail/yt-users-spacepope.org/attachments/20151007/bb176737/attachment.htm>