[yt-users] unit conversions

Nathan Goldbaum nathan12343 at gmail.com
Mon Jun 19 17:48:56 PDT 2017


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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.spacepope.org/pipermail/yt-users-spacepope.org/attachments/20170619/37184ac7/attachment.htm>


More information about the yt-users mailing list