[yt-users] YTSphereTooSmall

[Geoffrey So]

Yeah for the spheres I use the "Ones" to get a cell count.  I guess if I
just want the region around the halo I don't necessarily need to limit
myself to the sphere data object, it was just the first thing that came to
mind.

Thanks!

From
G.S.

On Wed, May 23, 2012 at 1:46 PM, Matthew Turk <matthewturk at gmail.com> wrote:

> Hi Geoffrey,
>
> On Thu, May 24, 2012 at 5:40 AM, Geoffrey So <gsiisg at gmail.com> wrote:
> > Stephen,
> >
> > I'm printing the warning message when along with the halo.id as the
> > exception is raised, so it appears that halo 5 in this case has a radius
> > smaller than dx, but what it really should be checking is the maximum
> > instead of the virial radius instead if I'm not mistaken.
> >
> > Matt,
> >
> > I just want the field attributes of where the halo is located, and I'm
> > comparing the attributes to the region surrounding the halo (up to 3x the
> > virial or maximum radius) to see if there's anything that is
> substantially
> > different.  I want to see what's different in the field quantity that
> > suppresses star formation in lower mass haloes.  In this analysis the
> > detailed shape and size of the sphere doesn't really matter, I'm just
> using
> > it as a data container.
> >
> > Right now I'm trying to output Density averaged values of each halo but
> > whenever I encounter a halo with radius smaller than a cell (triggering
> > YTSphereTooSmall), I output 0 for all attributes.  So I expect lots of
> zeros
> > to occur on the small end.  However I'm seeing some zeros scattered even
> in
> > the high mass end with large maximum radius, and I think the high mass
> halos
> > with zeros is the result of it having a small virial radius, at least
> that's
> > my current hypothesis.
> >
> > I'm going to try to go down the list from the high mass end to see if the
> > second halo giving me zeros on the high end also have a virial radius
> > smaller than dx.
> >
> > I guess a work around for this problem temporarily is to
> > use pf.h.sphere(halo.center_of_mass(), halo.maximum_radius()) instead of
> > calling halo.get_sphere().
>
> That makes sense!  Good luck.  One other option would be to take the
> halo center and construct a region, with:
>
> region = pf.h.region(halo_center, halo_center - dx*n_cells,
> halo_center + dx*n_cells)
>
> This will get you a rectangular prism.  (You'll need to set n_cells
> and dx.)  A quick way to see how many cells it contains is to take a
> look at region["Ones"].size, which should be very fast.
>
> -Matt
>
> >
> > From
> > G.S.
> >
> >
> > On Tue, May 22, 2012 at 6:16 PM, Stephen Skory <s at skory.us> wrote:
> >>
> >> Hi Geoffrey and Matt,
> >>
> >> > While I think Stephen might know why the difference between
> >> > maximum_radius / virial_radius is confusing the system here,
> >>
> >> I don't quite know what's going on. halo.get_sphere() should give you
> >> a YT sphere centered on the center of mass of the halo, with radius of
> >> .maximum_radius(). Perhaps it's not halo 5 that's giving you the
> >> error? Or there's an error in what you're printing?
> >>
> >> > I want to
> >> > suggest you back up a bit.  Do you really want to analyze halos that
> >> > are O(dx) across?
> >>
> >> I agree with Matt that you should take a close look at what you are
> >> asking from these halos, and if one or just a few cells are sufficient
> >> to give you that.
> >>
> >> --
> >> Stephen Skory
> >> s at skory.us
> >> http://stephenskory.com/
> >> 510.621.3687 (google voice)
> >> _______________________________________________
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> >
> >
> >
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