[yt-users] unit conversions

[Nathan Goldbaum]

On Tue, Jun 20, 2017 at 12:42 AM, Stephanie Tonnesen <stonnes at gmail.com>
wrote:

> Hi Nathan (and yt-users),
>
> Thanks!  Yes,
> arr_in_cm = ndarray_in_centimeters * cm
>
> got yt to see that I was talking about cm.
>
> The problem is that I still don't see the points.  Is there any example of
> putting points on a volume rendering?  I am trying to mix the "Volume
> Rendering with Lines" cookbook recipe with the PointSource api description,
> but am not sure what I am hoping my result will look like--for example, how
> big can I expect my points to be?  Is that something I can set?
>

Yup:

http://yt-project.org/docs/dev/cookbook/complex_plots.html#volume-rendering-with-points

It looks like PontSource optionally takes either a scalar or ndarray of
radii (one radius value for each point):

http://yt-project.org/docs/dev/reference/api/yt.visualization.volume_rendering.render_source.html#yt.visualization.volume_rendering.render_source.PointSource


>
> Thanks,
>
> Stephanie
>
>
>
>
> --
> Dr. Stephanie Tonnesen
> Alvin E. Nashman Postdoctoral Fellow
> Carnegie Observatories, Pasadena, CA
> stonnes at gmail.com
>
> On Mon, Jun 19, 2017 at 5:48 PM, Nathan Goldbaum <nathan12343 at gmail.com>
> wrote:
>
>> Hi Stephanie,
>>
>> If you have a loaded dataset, you can convert an ndarray that you know is
>> in centimeters to a YTArray in code_length units like so:
>>
>> arr_in_code_length = ds.arr(ndarray_in_centimeters,
>> 'cm').to('code_length')
>>
>> In addition, I don't think you actually need to convert to code_length
>> units if you are passing this array to yt, since yt will internally do the
>> conversion if you hand it a YTArray with units, so just creating an array
>> like this is sufficient:
>>
>> from yt.units import cm
>>
>> arr_in_cm = ndarray_in_centimeters * cm
>>
>> And then pass arr_in_cm to some yt function.
>>
>> If all you want is the conversion factor from CGS to code length units,
>> then you can inspect ds.length_unit. For example, the conversion from code
>> length units to CGS is ds.length_unit.in_cgs(). There are a number of unit
>> attributes that are attached to datasets (ds.mass_unit, ds.velocity_unit,
>> ds.pressure_unit) that are useful for this sort of thing.
>>
>> Hope that helps!
>>
>> -Nathan
>>
>> On Mon, Jun 19, 2017 at 7:38 PM, Stephanie Tonnesen <stonnes at gmail.com>
>> wrote:
>>
>>> Hi yt-users!
>>>
>>> I have what I think should be a relatively simple question.  I am trying
>>> to make a 3D image of a region of a cosmological simulation, and plot
>>> points in the image.  I define my region with box(left_edge,right_edge)
>>> where left_edge and right_edge are in code units.  However, the points that
>>> I read in from an earlier file are in cgs units.  Since the file was
>>> written using yt output, I would like to just let yt do the conversions,
>>> but nothing has units attached.  I want the 3d image to get everything into
>>> the same units.  I feel like there are a few ways I could fix this
>>> problem--1)  tell yt that my points are in cgs units, 2) force the
>>> create_scene to be in cgs units, 3) get yt to tell me the conversion factor
>>> from code units to cgs units.
>>>
>>> Unfortunately, I don't know how to do any of these things!
>>>
>>> Can someone give me some advice on what to do here?
>>>
>>> Thanks!
>>>
>>> Stephanie
>>>
>>> --
>>> Dr. Stephanie Tonnesen
>>> Alvin E. Nashman Postdoctoral Fellow
>>> Carnegie Observatories, Pasadena, CA
>>> stonnes at gmail.com
>>>
>>> _______________________________________________
>>> yt-users mailing list
>>> yt-users at lists.spacepope.org
>>> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>>
>>>
>>
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