Sorry Nick, I accidentally skipped over this question. The nearest neighbor deposit operation deposits a the field value of the particle closest to that cell's position - I don't think it's doing what you thought it was doing. Take a look at this modified version of your script: https://gist.github.com/ngoldbaum/a1ea4dc0c8cde6ca1630f251a350b110 It should output: 1625.2196373326824 Msun 2367.0651822468562 Msun 32518.862230804152 Msun 32518.862230804152 Msun 32518.862230804152 Msun Note that I'm running the development version of yt, where PR 1802 is merged (https://github.com/yt-project/yt/pull/1802), so I didn't need to FieldDetector stuff in the field definition. You can see that this is more or less how the ('deposit', 'foo_density') fields that automatically created by yt work: https://github.com/yt-project/yt/blob/be560338a0a144055706b8a4a3295606a3f25e... If you're interested in seeing more about how to use the low-level particle deposition API (i.e. bypassing ds.add_particle_field), that file is pretty rich with examples. On Fri, Jun 1, 2018 at 2:36 PM, Nick Gnedin wrote:

I wonder if this message could have been overlooked somehow.

On 05/27/2018 03:23 PM, Nick Gnedin wrote:

...

I also have a follow-up question. My previous question was about the build-in deposited fields. But when I try to do that myself, units seem to be screwed up.

----------------------- import yt import numpy as np

def StellarMass2(field,data): ms = data[('STAR','particle_mass')] if('FieldDetector' in str(type(data))): return ms else: return ms.in_units("Msun")

d = yt.load("rei10_a0.1001/rei10_a0.1001.art")

d.add_field(("STAR","mass2"),function=StellarMass2,sampling_type="particle",units="Msun")

d.add_deposited_particle_field(("STAR","mass2"),"nearest",weight_field='particle_ones')

xcen = d.arr([5,5,5],"Mpccm/h") s = d.sphere(xcen,(100,"kpc")) sf = ('STAR','mass2') df = ('deposit','STAR_nn_mass2') print(np.amax(s[sf]),np.amax(s[df])) ----------------------------

...

1625.2196373326824 Msun 1625.2196373326824 Msun

I.e, the units of the deposited field are that of mass, rather than density.

Even worse, if I treat the deposited field as the mass per cell rather than density, it does not add up:

print("sum=%9.3e int=%9.3e"%(np.sum(s[sf].in_un its("Msun")),np.sum(s[df].in_units("Msun"))))

...

sum=3.252e+04 int=1.521e+05

So, I am totally lost about what add_deposited_particle_field() function actually does.

n

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