[yt-users] Density / DMDensity

[ｔyuta]

Dear Nathan,

The particle filter worked well and I could read the star density from the
data. Thanks!
Now I want to subtract stellar mass density from Dark_Matter_Density. I was
trying to define a new field "only_DM", but it did not work. Could you tell
me what is wrong with this?

(jupiter notebook session)
import yt
from yt.data_objects.particle_filters import add_particle_filter

def stars(pfilter, data):
    filter = data[(pfilter.filtered_type, "particle_type")] == 2
    return filter

add_particle_filter("stars", function=stars, filtered_type='io',
                    requires=["particle_type"])

ds.add_particle_filter('stars')

def only_DM(field, data):
    return data['Dark_Matter_Density'] - data['deposit','stars_density']

ds=yt.load(".../redshift00??")

ds.add_field(("Dark_Matter_Density", "only_DM_Density"), units="kg/m**3",
function=only_DM)

and the error message appears:

YTFieldNotFound: Could not find field '('deposit', 'stars_density')'
in redshift00??.


Sincerely,

Y.T.


2017-10-11 16:24 GMT-04:00 Nathan Goldbaum <nathan12343 at gmail.com>:

> OK, in that case I wouldn't try to infer the stellar mass from the
> Dark_Matter_Density field (which does include stellar mass despite the
> name), instead I would define a particle filter for stars (
> http://yt-project.org/doc/analyzing/filtering.html#
> filtering-particle-fields) and then use the new particle type defined by
> the filter to create a deposited particle field (
> http://yt-project.org/doc/analyzing/fields.html#deposited-particle-fields
> ).
>
> There's an example in the docs for how to do this with Tipsy data here:
> http://yt-project.org/doc/cookbook/constructing_data_
> objects.html#creating-particle-filters
>
> For Enzo, you should use the particle_type field to create the filter -
> star particles in Enzo have particle_type equal to 2. Here's a short worked
> example:
>
> https://gist.github.com/anonymous/acd4007dbff283fc3587a47e8ba41dc3
>
> Hope that helps! And I hope to hear more from you - your name is
> particularly well suited to the yt project ;)
>
> -Nathan
>
>
> On Wed, Oct 11, 2017 at 12:58 PM, ｔyuta <y0u1t1a5.t at gmail.com> wrote:
>
>> Yes, it's Enzo data.
>>
>> 2017-10-11 10:17 GMT-04:00 Nathan Goldbaum <nathan12343 at gmail.com>:
>>
>>> What simulation code are you working with? From the field names it
>>> sounds like Enzo data.
>>>
>>> On Wed, Oct 11, 2017 at 9:13 AM ｔyuta <y0u1t1a5.t at gmail.com> wrote:
>>>
>>>> Dear yt-users,
>>>>
>>>> Hi, I'm a new user of yt. I have a question about the default 'Density'
>>>> field and 'Dark_Matter_Density' field. Do they contain stellar mass? If so,
>>>> how can I read and subtract stellar mass from the data?
>>>>
>>>> Sincerely,
>>>> Y.T.
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