Add set_XY and set_data to Quiver

[ianhi]

PR Summary

Will close #22402 and close #11790

still a bit of tidying up to do, and should probably pair with a similar implementation for Barb.

Opening early to get feedback I think I did all the shape setting correctly, but not entirely clear whats happening with all the masking. Also this will enable modifying the number of points and there was originally some concern about that.

Example script:

import matplotlib.pyplot as plt
import numpy as np

X, Y = np.random.rand(10, 2).T
U, V = np.random.rand(10, 2).T

fig, ax = plt.subplots()
Q = ax.quiver(X, Y, U, V)

plt.show(block=False)
plt.pause(2)

X, Y, U, V, C = np.random.rand(11, 5).T
Q.set_data(X, Y, U, V, C)
fig.canvas.draw()
plt.show(block=True)

PR Checklist

Tests and Styling

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).

[jklymak]

The API seems fine, though I wonder about providing the conveniences, versus just set_data. Why does your example need a fig.canvas.draw? (= fig.draw_without_rendering)

[ianhi]

The API seems fine, though I wonder about providing the conveniences, versus just set_data.

I put in both since set_UVC already exists although i suppose instead that could be deprecated?

fig.canvas.draw? (= fig.draw_without_rendering)

I'm a bit confused. the example changes after some time so since it's displayed already you need to call draw to update it

[jklymak]

I dont think of fig.canvas.draw as user-facing.

[ianhi]

fig.canvas.draw (or draw_idle) is crucial when doing anything interactive with set_data etc. For example see the slider examples: https://matplotlib.org/stable/gallery/widgets/slider_demo.html or https://matplotlib.org/stable/gallery/animation/strip_chart.html?highlight=codex%20fig%20canvas%20draw here it's necessary to update the figure because the second show doesn't force a draw.

[oscargus]

Remove "only"? (Does three count as only?)

Single back-ticks will link, right? I guess one should be consistent with either using () for all or none of the methods.

[oscargus]

Couldn't comment in the source, but Barbs has this in the docs:

The only API method is :meth:`set_UVC`, which can be used to

which no longer is correct.

[oscargus]

I think this would be nice to get into 3.7. Would you have time to update it?

I guess one can use the docs of the original Quiver class to explain the U, V, and C arguments in set_data.

[ianhi]

I think this would be nice to get into 3.7. Would you have time to update it?

maybe - when is the deadline there? jan 1?

Also dependent on figuring out what I meant by:

still a bit of tidying up to do

also

and should probably pair with a similar implementation for Barb.

probably won't be able to do that

[ianhi]

note to self - this is part of the "cleaning up"

[oscargus]

maybe - when is the deadline there? jan 1?

As I understand it, yes, but with some margins.

[timhoffm]

and should probably pair with a similar implementation for Barb.

probably won't be able to do that

We can still do that later. Already having this on Quiver is an improvement, and I assume Barb is less often used compared to Quiver.

[jklymak]

@ianhi I'll move to Draft until you have time to come back to this...

[QuLogic]

This was replaced by #26410.