[yt-users] unit conversions

[Nathan Goldbaum]

On Tue, Jun 20, 2017 at 1:00 AM, Nathan Goldbaum <nathan12343 at gmail.com>
wrote:

>
>
> 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
>

And the radii must be given in pixels. I guess we should probably improve
this API to handle units better.


>
>
>>
>> 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
>>>>
>>>>
>>>
>>> _______________________________________________
>>> yt-users mailing list
>>> yt-users at lists.spacepope.org
>>> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>>
>>>
>>
>> _______________________________________________
>> yt-users mailing list
>> yt-users at lists.spacepope.org
>> http://lists.spacepope.org/listinfo.cgi/yt-users-spacepope.org
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.spacepope.org/pipermail/yt-users-spacepope.org/attachments/20170620/9476dcea/attachment.html>