Add weights and axis parameters to vonmisesmle

[FelipeCybis]

Add weights and axis parameters to vonmisesmle

This pull request is to address the lack of "weights" and "axis" parameters on the circstats function vonmisesmle.
The "axis" parameter that existed but was not actually being used allows for fast usage of 2D numpy arrays.
The "weights" parameter is very convenient since it is very common to have data for binned angles.

The appropriate tests were added to test_circstats.test_vonmisesmle in 4c6172f, but here is a minimum example using scipy's vonmises PDF:

>>> from astropy import stats
>>> import scipy
>>> x = np.linspace(0,2*np.pi,100)
>>> mu, kappa = stats.circstats.vonmisesmle(x, weights=scipy.stats.vonmises.pdf(x, loc = np.pi/2, kappa=4))
>>> mu, kappa
(1.56976133088732, 3.9514188541707314)

Or for 2D arrays:

>>> x = np.linspace(0,2*np.pi,100)
>>> xx = np.tile(x, [4,1])*u.rad
>>> vm = np.stack([
    scipy.stats.vonmises.pdf(x, loc = np.pi/2, kappa=4),
    scipy.stats.vonmises.pdf(x, loc = np.pi/2, kappa=1),
    scipy.stats.vonmises.pdf(x, loc = np.pi/4, kappa=4),
    scipy.stats.vonmises.pdf(x, loc = np.pi/8, kappa=8)])
>>> stats.circstats.vonmisesmle(xx, weights=vm, axis=1)
(<Quantity [1.56976133, 1.55292537, 0.77316812, 0.37759809] rad>,
 <Quantity [3.95141885, 0.98695686, 3.91289117, 7.95905254]>)

Fixes # There is not opened issue, since it is an enhancement.

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[pllim]

Thanks, you might also be interested in the discussions at #13749

[pllim]

I would rephrase the change log text to the tone of what you want user to know about the changes when they read the release change log. They would not care it was from a pull request. Feel free to look at existing change log texts for examples. Thanks!

[FelipeCybis]

Thanks for directing me to #13749. Indeed, could be interesting taking the best of both packages in the long run. Particularly I could certainly not work without weighing my arrays (hence the PR ;)). Also if you guys decide on adapting the kappa estimation using the scipy method it should be straight forward with the weights and axis params.

Also, tell me if I can still improve this PR in some way :)

[pllim]

Are these supposed to be bullet points? @saimn , does towncrier render bullets properly?

[FelipeCybis]

Indeed, I should have put a line between the paragraph and the bullet points. I don't know about towncrier, but if it handles .rst it should handle bullet points?
I can delete these two points all around. If the user knows how to use the weights and axis for the rest of the module, they will understand the idea of the change?
Up to you, I can either remove them or add the line between paragraph and bullet points

[FelipeCybis]

BTW, I finally deleted the bullet points as they were not adding much to the change log indeed.

[pllim]

@FelipeCybis , sorry for the delay. Coverage is still complaining but the log is too old now, so I cannot see if the coverage upload failed or is it because of something else. Could you please rebase?

@larrybradley , are you able to review this before feature freeze?

Thanks!

[larrybradley]

Thanks, @FelipeCybis. LGTM, with one minor requested change.

[pllim]

pre-commit.ci autofix

[pllim]

Seems like black overdid it a little but this is what would make the precommit bot happy. 🤷

[larrybradley]

I really don't like this formatting. We could manually reformat and turn off black (fmt: off), but let's just get this in before the freeze.

[larrybradley]

Thanks, @FelipeCybis

[pllim]

Thanks, all!