Hi Nathan,

Thanks for your hard work on this PR (along with Ben Thompson). The naming convention that I suggested in the issue a few weeks back (https://bitbucket.org/yt_analysis/yt/issue/947/consistent-field-naming-for-spherical-and) and in the discussion on your PR also matches with past convention. It is slightly different than what you propose, but seems (to me at least) to be more easy to read because the adjective comes before the noun (e.g. spherical position) instead of the reverse (e.g. position spherical).

Where proposed naming convention #1 is:

(field_type, "<particle?>_<position/velocity>_<coordinate_system>_<coordinate>") e.g. ('all', 'particle_position_spherical_phi')

Proposed naming convention #2 is:

(field_type, "<particle?>_<coordinate_system>_<position/velocity>_<coordinate>") e.g. ('all', 'particle_spherical_position_phi')

Here are all of the relevant gas and particle fields each convention:

Cartesian (convention #1 & #2 are the same)

('index', 'x')

('index', 'y')

('index', 'z')

('gas', 'velocity_x')

('gas', 'velocity_y')

('gas', 'velocity_z')

('all', 'particle_position_x')

('all', 'particle_position_y')

('all', 'particle_position_z')

('all', 'particle_velocity_x')

('all', 'particle_velocity_y')

('all', 'particle_velocity_z')

Convention #1 & #2 differ for the fields of cartesian position relative to the 'center' and 'normal' field parameters for the origin and z-vector:

#1 vs #2

('all', 'particle_position_relative_x') vs. ('all', 'particle_relative_position_x')

('all', 'particle_position_relative_y') vs. ('all', 'particle_relative_position_y')

('all', 'particle_position_relative_z') vs. ('all', 'particle_relative_position_z')

('all', 'particle_velocity_relative_x') vs. ('all', 'particle_velocity_position_x')

('all', 'particle_velocity_relative_y') vs. ('all', 'particle_velocity_position_y')

('all', 'particle_velocity_relative_z') vs. ('all', 'particle_velocity_position_z')

Spherical:

#1 vs #2

('index', 'spherical_phi')

('index', 'spherical_radius')

('index', 'spherical_theta')

('gas', 'velocity_spherical_phi') vs ('gas', 'spherical_velocity_phi')

('gas', 'velocity_spherical_theta') vs ('gas', 'spherical_velocity_theta')

('gas', 'velocity_spherical_radius') vs ('gas', 'spherical_velocity_radius')

('all', 'particle_position_spherical_phi') vs ('all', 'particle_spherical_position_phi')

('all', 'particle_position_spherical_theta') vs ('all', 'particle_spherical_position_theta')

('all', 'particle_position_spherical_radius') vs ('all', 'particle_spherical_position_radius')

('all', 'particle_velocity_spherical_phi') vs ('all', 'particle_spherical_velocity_phi')

('all', 'particle_velocity_spherical_theta') vs ('all', 'particle_spherical_velocity_theta')

('all', 'particle_velocity_spherical_radius') vs ('all', 'particle_spherical_velocity_radius')

Cylindrical:

#1 vs #2

('index', 'cylindrical_phi')

('index', 'cylindrical_radius')

('index', 'cylindrical_theta')

('gas', 'velocity_cylindrical_phi') vs ('gas', 'cylindrical_velocity_phi')

('gas', 'velocity_cylindrical_theta') vs ('gas', 'cylindrical_velocity_theta')

('gas', 'velocity_cylindrical_radius') vs ('gas', 'cylindrical_velocity_radius')

('all', 'particle_position_cylindrical_phi') vs ('all', 'particle_cylindrical_position_phi')

('all', 'particle_position_cylindrical_theta') vs ('all', 'particle_cylindrical_position_theta')

('all', 'particle_position_cylindrical_radius') vs ('all', 'particle_cylindrical_position_radius')

('all', 'particle_velocity_cylindrical_phi') vs ('all', 'particle_cylindrical_velocity_phi')

('all', 'particle_velocity_cylindrical_theta') vs ('all', 'particle_cylindrical_velocity_theta')

('all', 'particle_velocity_cylindrical_radius') vs ('all', 'particle_cylindrical_velocity_radius')

So what does the community think would be the best system here? #1 or #2? Either way it goes, I think this is a big improvement over the previous naming convention that had general inconsistencies.

Cameron

On Tue, Dec 23, 2014 at 11:01 AM, Nathan Goldbaum <nathan12343@gmail.com> wrote:

Hi all,

I've just issued a pull request that bears some developer discussion.

Right now yt is a bit of a wild west in terms of the field naming convention for fields that reference a coordinate system. See for example, see issue 947:

https://bitbucket.org/yt_analysis/yt/issue/947/consistent-field-naming-for-spherical-and

I'd like to propose a naming convention for fields that reference a coordinate system. Gas and particle fields should be of the form:

(field_type, "<particle?>_<vector_field_name>_<coordinate>")

while index fields for coordinates should be of the form:

("index", "<coordinate>")

This fits within our existing field naming convention for cartesian coordinates, e.g.:

("gas", "velocity_x")
(ptype, "particle_velocity_y")

as well as our convention for index coordinate fields, e.g.:

("index", "x")
("index", "spherical_theta")

This means that index fields do not need to explicitly reference themselves as positions. So we *won't* have field names like:

("index", "position_x")

I don't like the above construction because it's a bit redundant ("index" implies that we are talking about a position or something similar).

Some existing field names will need to be changed to fit this. In particular, some of the index fields will need to be renamed to be more verbose ("index", "spherical_r") becomes ("index", "spherical_radius") and (ptype, "particle_spherical_position_radius") becomes (ptype, "particle_position_spherical_radius").

Wherever an existing field name needs to change, I propose we mark the existing field name for deprecation, stub it out, and make it an alias for the field with the new field name. In a future release, we can then remove the deprecated fields.

I've implemented this for the particle fields (for the most part) in PR 1378:

https://bitbucket.org/yt_analysis/yt/pull-request/1378

I'm happy to update the field naming YTEP if this proposed field naming scheme gets approval in this thread.

What do you all think? Question, concerns?

-Nathan

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Cameron Hummels

Postdoctoral Researcher

Steward Observatory

University of Arizona

http://chummels.org