Hi HyeonYong,

Can you try two things for me?

1) Add the fields before you create the dataset. Instead of accessing the star count etc outside of it, access it like:

data.ds.whatever

so that it gets dynamically called each time. 2) Return a newly allocated array each time, instead of a copy of an external array.

There's also the possibility that there will be issues with "sub-chunking" where the subsets of data don't line up. I think I have an idea for that case, but I want to see if these will work first.

Thanks,

Matt

On Mon, Mar 28, 2022 at 1:27 PM HyeonYong Kim gusdyd398@snu.ac.kr wrote:

Hi, everyone

I want to utilize data using ds.region function. I have used the CHANGA code-Tipsy dataset, which has 3 particle types - Gas, Stars, Darkmatter. Because there is no particle index, so I added a field this way.

            ds=yt.load("My data~~")
            gas_num=np.shape(ds.all_data()['Gas','Mass'])[0]              #number of gas particle
            star_num=np.shape(ds.all_data()['Stars','Mass'])[0]            #number of star particle
            dm_num=np.shape(ds.all_data()['DarkMatter','Mass'])[0]  #number of darkmatter particle
            gas_index=range(gas_num)                                                                      #gas index
            star_index=range(gas_num,gas_num+star_num)                                      #star index
            dm_index=range(gas_num+star_num,gas_num+star_num+dm_num)     #darkmatter index
            all_index=range(gas_num+star_num+dm_num)
            def _gas_index(field,data):                                   #define index field
                return (ds.arr(gas_index))
            def _star_index(field,data):
                return (ds.arr(star_index))
            def _dm_index(field,data):
                return (ds.arr(dm_index))
            def _all_index(field,data):
                return (ds.arr(all_index))
            yt.add_field(
                name=("Gas", "particle_index"),
                function=_gas_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            ds.add_field(
                name=("Gas", "particle_index"),
                function=_gas_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            yt.add_field(
                name=("Stars", "particle_index"),
                function=_star_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            ds.add_field(
                name=("Stars", "particle_index"),
                function=_star_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            yt.add_field(
                name=("DarkMatter", "particle_index"),
                function=_dm_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            ds.add_field(
                name=("DarkMatter", "particle_index"),
                function=_dm_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            yt.add_field(
                name=("all", "particle_index"),
                function=_all_index,
                sampling_type="particle",
                units="(dimensionless)",
            )
            ds.add_field(
                name=("all", "particle_index"),
                function=_all_index,
                sampling_type="particle",
                units="(dimensionless)",
            )

and then, I made a sphere region to select data in this region. However, the problem is although I made the regions, particle_index returns all datasets.

sp=ds.sphere(center,(radius,"kpc"))
len(ds.all_data()["DarkMatter","particle_mass"])
-->19584552
len(sp["DarkMatter","particle_mass"])
-->1287749

this is what I expected, but

len(ds.all_data()["DarkMatter","particle_index"])
-->19584552
len(sp["DarkMatter","particle_index"])
-->19584552

the particle_index field returns the same value. It seems that this is because I just used array when I define the field function, but I don't have an idea.

I would appreciate it if anyone can give me some favors. Thank you for reading!

Sincerely, HyeonYong _______________________________________________ yt-users mailing list -- yt-users@python.org To unsubscribe send an email to yt-users-leave@python.org https://mail.python.org/mailman3/lists/yt-users.python.org/ Member address: matthewturk@gmail.com