[yt-users] dynamic derived fields

Matthew Turk matthewturk at gmail.com
Wed May 12 06:55:08 PDT 2010


Hi Charles,

I like Britton's suggestions, but you can also try out the
field_parameters stuff:

http://yt.enzotools.org/doc/howto/creating_derived_fields.html?highlight=set_field_parameter#some-more-complicated-examples

-Matt

On Wed, May 12, 2010 at 6:17 AM, Britton Smith <brittonsmith at gmail.com> wrote:
> Hi Charles,
>
> I think you could do this in a couple ways.  The data argument in field
> functions gives you access to the parameter file of the dataset (data.pf).
> One thing you can do is set your own parameters in the pf that can later be
> used by your function.  So you could do:
> pf = load(dataset)
> pf.parameters['temperature_threshold'] = 1.e7
> Then, inside your field function, you'll have access to that value as
> data.pf.parameters['temperature_threshold'].
>
> The other way would be to embed the definition of the field function and the
> call to add_field within another function that takes temperature_threshold
> as an argument.  You can call that function over and over and it should
> overwrite the previous definition of the field.
>
> Britton
>
> On Wed, May 12, 2010 at 1:24 AM, Charles Hansen <chansen at astro.berkeley.edu>
> wrote:
>>
>> Hi all,
>>
>> Is it possible to make something like a derived field in yt that takes
>> passed variables?  A simple example would be extracting gas density above a
>> certain temperature, but changing that temperature threshold on the fly
>>
>> def _hotgas(field, data, temperature_threshold):
>>   reutrn data["density"]*(data["Temperature"] > temperature_threshold)
>> add_field("hotgas", function=_hotgas, Something else goes here?)
>>
>> In this particular case I only need a few temperatures and can make a new
>> derived quantity each time, but it seems like a generally useful ability.
>>
>> Thanks,
>> Charles
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>
>
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