[yt-dev] Microns & Simulation-Specific Unit Base

[John ZuHone]

Hi Axel,

You can assign new symbols as well. It sounds like you want to do this for a number of datasets, so you could define new symbols and add them to yt’s unit registry (though you could also add them to a specific dataset’s unit registry). To do the former, you could do something like this in your plugins [1] file (which would ensure they got loaded every time you used yt):

```python
from yt.units.unit_object import default_unit_registry
from yt.units import dimensions

default_unit_registry.add("lambda_0", 8.0e-5, dimensions.length, 0.0, r"$\lambda_0$")
default_unit_registry.add("omega_pe", 1.0e15, dimensions.rate, 0.0, r"$\omega_\text{pe}$") 
```

The arguments in .add are the name of the symbol, the conversion to CGS+Ampere, the dimensions of the unit, the unit offset (only used for temperature and angle units), and the last is the LaTeX representation. 

Note that I defined omega_pe as a rate, so you’d have to use its inverse when creating your unit system to define the base time units.

And yes, as I mentioned above the internal base by which all yt units reference is cgs units + Amperes for current (for historical reasons, mostly). 

Best,

John

[1] http://yt-project.org/doc/reference/configuration.html#the-plugin-file <http://yt-project.org/doc/reference/configuration.html#the-plugin-file>

> On Jan 5, 2017, at 8:24 AM, Axel Huebl <a.huebl at hzdr.de> wrote:
> 
> Ha, I oversaw a link in [1] linking to [2].
> 
> Ok, so I can just specify my own unit system in user-code with that.
> But anyhow, I can't assign it new symbols. Also, do all conversion
> factors need to go through CGS?
> 
> Also, microns turns out to be
>   .in_units("um")
> :)
> 
> 
> Axel
> 
> [2] http://yt-project.org/docs/dev/analyzing/units/unit_systems.html
> 
> On 05.01.2017 13:59, Axel Huebl wrote:
>> Hi yt-devs!
>> 
>> I have a quick user-question (sorry) and a devel question:
>> 
>> First, how to convert to a unit like microns (10^-6 meters) or
>> pico-seconds? I can't find an example here [1]. I tried
>> 
>>  .in_units("mum")
>>  .in_units("mu m)
>>  .in_units("1.e-6 m")
>>  .in_units("microns")
>>  .in_units("micro meter")
>>  .in_units("micro meters")
>>  .in_units("micro m")
>>  .in_units("μm")
>> 
>> and only
>>  .in_units("1.e-6 * m")
>> 
>> does not fail but looks ugly.
>> 
>> An orthogonal question: in our domain (laser-plasma physics) unit
>> systems are scaled by something like the applied laser wavelength or the
>> plasma density (and more to make a full set).
>> 
>> Following again [1] I would implement something like .in_base('plasma')
>> or .in_base('laserplasma') but those are not scaled to "fixed" reference
>> quantities as the other base systems but are depending on either user input
>>  [ length = ("$\lambda_0$", "800 nm"),
>>    time   = ("$\omega_\text{pe}^{-1}$", "1.e-15 s"),
>>     ...]
>> or alternatively scalings the data file already provided. (Ok, the
>> symbol is always fixed per "in_base" but the value to scale with needs
>> to be provided.)
>> 
>> Is that already possible or any ideas how we could implement that?
>> 
>> 
>> Thanks,
>> Axel
>> 
>> [1]
>> http://yt-project.org/docs/dev/analyzing/units/fields_and_unit_conversion.html#data-selection-and-fields
>> 
> 
> -- 
> 
> Axel Huebl
> Phone +49 351 260 3582
> https://www.hzdr.de/crp
> Computational Radiation Physics
> Laser Particle Acceleration Division
> Helmholtz-Zentrum Dresden - Rossendorf e.V.
> 
> Bautzner Landstrasse 400, 01328 Dresden
> POB 510119, D-01314 Dresden
> Vorstand: Prof. Dr.Dr.h.c. R. Sauerbrey
>          Prof. Dr.Dr.h.c. P. Joehnk
> VR 1693 beim Amtsgericht Dresden
> _______________________________________________
> yt-dev mailing list
> yt-dev at lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.spacepope.org/pipermail/yt-dev-spacepope.org/attachments/20170105/9e1bf7c6/attachment.htm>