[yt-users] Profile of a projected quantity?

Matthew Turk matthewturk at gmail.com
Sun May 4 10:34:50 PDT 2014


Hi Britton,

On Sun, May 4, 2014 at 9:25 AM, Britton Smith <brittonsmith at gmail.com> wrote:
> It would be cool if we were able to treat a projection as a 2D data
> container where you could define a center, create a radius field, and then
> just pipe directly into the regular profiling machinery.  How hard would it
> be to do that (longer timescale than meeting Nathan's needs here of course)?

I agree.  So I think the only reason this would be difficult is
because of the degeneracy between asking for a derived field that
would be derived *in the grids* and asking for a derived field that
would be derived *in the data object*.  Typically, we always assume
that the data object can generate derived fields -- effectively, what
this means is that if you ask for velocity magnitude, the velocity
magnitude can be derived from the x-y-z velocities in the data object
and that it doesn't need to go back to the individual
chunks/grids/particles.  This is how slices work, but projections
don't because we assume the act of projecting is how the data is
generated.  ("Construction" versus "selection" data objects.)

So if we can break that degeneracy -- having a way to say, this object
*has* everything we need to do the derived fields, so do them in it,
then I think we can implement it.  I think it's mostly a nomenclature
thing.  What if we were able to make projections serve as a source to
another data object?  Would that suffice?

>
>
> On Thu, May 1, 2014 at 2:34 PM, Nathan Goldbaum <nathan12343 at gmail.com>
> wrote:
>>
>>
>>
>> On Thu, May 1, 2014 at 8:07 AM, Cameron Hummels <chummels at gmail.com>
>> wrote:
>>>
>>> I have some scripts for doing projected radius profiles using projections
>>> and FRBs.  They'll certainly be different from the Profile1D stuff, but they
>>> work OK.  I'm happy to share them if you want a starter for this avenue.
>>
>>
>> Would love to see them.
>>
>>>
>>>
>>> Cameron
>>>
>>>
>>> On Wed, Apr 30, 2014 at 6:24 PM, Matthew Turk <matthewturk at gmail.com>
>>> wrote:
>>>>
>>>> Hi Nathan,
>>>>
>>>> On Wed, Apr 30, 2014 at 8:35 PM, Nathan Goldbaum <nathan12343 at gmail.com>
>>>> wrote:
>>>> > Hi all,
>>>> >
>>>> > Is there a way for me to find a profile using a projection as a data
>>>> > source?
>>>> > In particular, I'd like to find a radial profile of a surface density
>>>> > in a
>>>> > disk galaxy simulation.
>>>> >
>>>> > I think I could do this by histogramming a fixed resolution buffer
>>>> > created
>>>> > by a projection data source but is that the only way to do it?  I'd
>>>> > prefer
>>>> > for my data pipeline to look identical for computing profiles and in
>>>> > all
>>>> > other cases I'm using a Profile1D object to find things like the
>>>> > cumulative
>>>> > mass or the average density as a function of radius.
>>>>
>>>> I believe this is what has been done in the past -- Sam wrote a set of
>>>> scripts that did it this way.  I think, though, that you might be able
>>>> to use the cylindrical radius derived fields and then accumulate
>>>> within them.  Would that get to where you want the analysis?
>>>>
>>>> -Matt
>>>>
>>>> >
>>>> > Thanks for your help with this!
>>>> >
>>>> > -Nathan
>>>> >
>>>> > _______________________________________________
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>>>
>>>
>>>
>>>
>>> --
>>> Cameron Hummels
>>> Postdoctoral Researcher
>>> Steward Observatory
>>> University of Arizona
>>> http://chummels.org
>>>
>>> _______________________________________________
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>>>
>>
>>
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