Clarifying local descriptors in documentation

[scmartin]

Description

The environment.LocalDescriptors documentation doesn't really give a description of what the local descriptors are, how they are calculated, or even a reference that explains what they are. As far as I can tell, one would have to actually look through the source code to find out what this class actually calculates. In a previous version of the documentation there was this example but it is no longer in the 'stable' branch. The documentation for this class should be more explicit about what it calculates and what its properties are.

Motivation and Context

As an end user, it is hard to know whether and how to use classes like this without more information about what they are calculating.

[bdice]

I agree this documentation (https://freud.readthedocs.io/en/latest/modules/environment.html#freud.environment.LocalDescriptors) can be improved. The publication that developed and used this feature is "Machine learning for crystal identification and discovery" by Matthew Spellings and Sharon C. Glotzer. https://doi.org/10.1002/aic.16157 cc: @klarh

[bdice]

@scmartin The example you mentioned has changed URLs, but is still a part of the docs.

• Latest: https://freud.readthedocs.io/en/latest/gettingstarted/examples/module_intros/environment.LocalDescriptors.html
• v2.11.0 (latest at time of writing): https://freud.readthedocs.io/en/v2.11.0/gettingstarted/examples/module_intros/environment.LocalDescriptors.html