[yt-dev] Boolean data objects in yt-3

[Nathan Goldbaum]

On Friday, June 10, 2016, Brian O'Shea <bwoshea at gmail.com> wrote:

> Hi Nathan,
>
> I've stumbled across across a research task that could really use yt's
>>> Boolean data object feature, and according to the documentation it is not
>>> implemented in yt-3.  Have boolean data objects been replaced by something
>>> else?  I know there are various filtering methods in yt, but what I really
>>> need to do is spatial filtering (i.e., data in a sphere with some chunks of
>>> the sphere excised).
>>>
>>
>> This hasn't been implemented.
>>
>>
>>>
>>> In principle I'd be happy to take a crack at re-implementing it,
>>> although I might need some help.  Could somebody give me a sense of why it
>>> wasn't ported to yt-3 when the changeover was made?
>>>
>>
>> The data selection API was completely rewritten.
>>
>
> How difficult might it be to re-implement the boolean data objects in the
> new data selection API?  (I suppose the question is really "how difficult
> might it be for somebody who is a decent programmer but not an expert in
> yt's internals to do so"?)
>

I'm not sure, offhand. Probably very hard if you want to use the eval-style
way of contrusting the data objects using a string written in Python, since
data selection happens at a lower level in yt now. See
selection_routines.pyx for more details about how this works.

It is possible to combine data objects by chaining data_source keyword
arguments, (e.g. one can create a half-sphere data object by chaining a
region that selects only half a sphere with a sphere data object). It may
be possible to generalize that somehow.


>
> --Brian
>
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