[Yt-dev] filters for DerivedQuantities

[John Wise]

Hi Sam,

That's clever :)  Thanks for the tip.  I'll try this method out.

John

On 26 Aug 2010, at 10:27, Sam Skillman wrote:

> Hi John,
> 
> I think you could also do something similar with a 1D profile, though it isn't quite as easy to dial in an exact limit:
> 
> http://yt.enzotools.org/doc/api/generated/plot_types/yt.raven.PlotCollection.add_profile_object.html?highlight=add_profile#yt-raven-plotcollection-add-profile-object
> 
> where you define the whole box as the region you care about and then do:
> # Get the whole box
> reg = pf.h.all_data()
> 
> # Make the profile
> metal_mass = pc.add_profile_object(reg, ["Metallicity", "CellMass"])
> 
> # Get some easy pointers to the profile data
> bins = metal_mass.data._bins
> mass = metal_mass.data["CellMass"]
> 
> #  Now get total mass with Metallicity above a 1.0e-4 by getting the number of 
> mass_frac = mass[bins>1.0e-4].sum()/mass.sum()
> 
> That should give you something close to what you'd want.  You may want to increase the number of xbins if you want higher accuracy answer.  Finally, I'll just make a quick note that the profile creation can be done in parallel as long as lazy_reader=True, which it is by default.  
> 
> There may be other ways to do this as well, but this is what I'd probably do.
> 
> Best,
> Sam
> 
> On Thu, Aug 26, 2010 at 7:00 AM, John Wise <jwise at astro.princeton.edu> wrote:
> Hi,
> 
> I wanted to calculate volume filling fractions and mass fractions of gas that met some criteria.  Specifically, the fractions that have a certain metallicity.  The _Action routine looked promising, but I couldn't figure out how to use it.  I remember there was some talk about filters on the list, but I searched and found that it concerned the halo finder.
> 
> I might have reinvented the wheel, but this is how I did it.
> 
> http://paste.enzotools.org/show/1125/
> 
> It's basically _TotalQuantity with a filter.  Also I wanted it to accept multiple limits to avoid re-reading the data for every filter.
> 
> Was there an easier way to do this?
> 
> Thanks,
> John
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> 
> 
> -- 
> Samuel W. Skillman
> DOE Computational Science Graduate Fellow
> Center for Astrophysics and Space Astronomy
> University of Colorado at Boulder
> samuel.skillman[at]colorado.edu
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