Axes.inset_axes: enable Axes subclass creation #22608

rcomer · 2022-03-05T21:45:10Z

PR Summary

Modify Axes.inset_axes so it can accept the polar, projection and axes_class keywords, and therefore return subclasses of Axes. My target use-case is with Cartopy, so we can now adapt this gallery example to do something like

import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import numpy as np

def sample_data(shape=(73, 145)):
    """Return ``lons``, ``lats`` and ``data`` of some fake data."""
    nlats, nlons = shape
    lats = np.linspace(-np.pi / 2, np.pi / 2, nlats)
    lons = np.linspace(0, 2 * np.pi, nlons)
    lons, lats = np.meshgrid(lons, lats)
    wave = 0.75 * (np.sin(2 * lats) ** 8) * np.cos(4 * lons)
    mean = 0.5 * np.cos(2 * lats) * ((np.sin(2 * lats)) ** 2 + 2)

    lats = np.rad2deg(lats)
    lons = np.rad2deg(lons)
    data = wave + mean

    return lons, lats, data


lons, lats, data = sample_data()

ax = plt.subplot(111, projection=ccrs.PlateCarree())
ax.contourf(lons, lats, data)
ax.coastlines()

axins = ax.inset_axes([0.5, 0.03, 0.47, 0.47], projection=ccrs.PlateCarree())
axins.contourf(lons, lats, data)
axins.set_xlim(-10, 5)
axins.set_ylim(50, 60)
axins.coastlines()

box, lines = ax.indicate_inset_zoom(axins, edgecolor="black")

plt.show()

PR Checklist

Tests and Styling

Has pytest style unit tests (and pytest passes). I'm unsure what extra tests should be added for this. Advice welcome!
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).
[N/A] 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).

rcomer · 2022-03-05T22:13:00Z

Looks like I have broken one test consistently across platforms. I will have to come back to this another day.

jklymak · 2022-03-05T23:16:24Z

Inset axes are explicitly children of their parent axes so please don't also add the figure as a parent. I'm not quite sure what the best way to get a projection into an inset_axes is...

greglucas · 2022-03-06T03:14:45Z

This seems like a useful thing to have available in some form. Might be worth having a look at #22060 and whether https://github.com/matplotlib/matplotview would work with GeoAxes too...

Ahh, the axes being a child of the figure or not would actually explain why mpl_toolkit inset_axes warn with tight_layout() (because they are added!), but standard inset_axes don't. (xref: #22611)

matplotlib/lib/mpl_toolkits/axes_grid1/inset_locator.py

Line 294 in e75b529

parent_axes.figure.add_axes(inset_axes)

The easiest way might be to allow axes_class to be passed in to the inset_axes() method, similar to mpl_toolkits and figure's add_axes methods.

matplotlib/lib/mpl_toolkits/axes_grid1/inset_locator.py

Lines 380 to 385 in e75b529

    
               axes_class : `matplotlib.axes.Axes` type, default: `.HostAxes` 
        
                   The type of the newly created inset axes. 
        
               axes_kwargs : dict, optional 
        
                   Keyword arguments to pass to the constructor of the inset axes. 
        
                   Valid arguments include:

However, there might be some more surgery needed outside of AxesGrid to support the projection or other keyword args.

matplotlib/lib/matplotlib/figure.py

Lines 535 to 538 in 09b17b1

    
                   axes_class : subclass type of `~.axes.Axes`, optional 
        
                       The `.axes.Axes` subclass that is instantiated.  This parameter 
        
                       is incompatible with *projection* and *polar*.  See 
        
                       :ref:`axisartist_users-guide-index` for examples.

rcomer · 2022-03-06T08:40:45Z

Thanks for the feedback. I did have a hunch that it couldn't really be this simple!

Inset axes are explicitly children of their parent axes so please don't also add the figure as a parent.

I'm afraid I don't have the background knowledge to understand this. Is there somewhere I can read up on the matplotlib parent/child relationships and why they matter? I guess the comment about tight_layout gives a clue.

matplotlibview

Looks useful - thanks! I will have a play with that at some point.

The easiest way might be to allow axes_class to be passed in to the inset_axes() method, similar to mpl_toolkits and figure's add_axes methods.

I'm not so keen on that API as it seems inconsistent with how the user is usually encouraged to create their Axes instances. But I guess it was done in those other functions for a reason.

Anyway it seems that whatever the answer is, it's not this. So for now I will just close this.

jklymak · 2022-03-06T19:05:19Z

@rcomer, maybe convert this to an issue? I think it is reasonable to ask that inset_axes accepts projections, I'm just not sure off the top of my head how to do it (I have limited Matplotlib (and internet) bandwidth at the moment.

rcomer · 2022-03-09T15:11:13Z

maybe convert this to an issue?

Issue now at #22630. Thanks!

rcomer · 2022-03-18T16:17:06Z

The important functionality seems to be contained within Figure._process_projection_requirements, so I tried using that directly. The Cartopy example still works, so I just wanted to see how it would fly with the CI.

jklymak · 2022-03-25T12:55:51Z

@rcomer, did this not work? It looks like something similar should work, and it is certainly reasonable functionality...

rcomer · 2022-03-25T13:07:56Z

@jklymak yes the CI all seemed fine and it works for my Cartopy example. However at #22630 @mylasem said they were working on it, so I thought I would leave it to them for now. I'd be happy to pick this up again at some point if @mylasem's version doesn't land for whatever reason.

jklymak · 2022-03-25T14:26:19Z

In general, Matplotlib does not have a "reserve an issue" policy, and this PR predates @mylasem 's comment. I think they should work within the context of this PR if at all possible.

rcomer · 2022-03-31T09:28:26Z

OK, since @mylasem has not commented further and I had some time, I have:

Added some basic tests to verify that the expected type is returned for our three methods of specifying it.
Updated the Axes.inset_axes docstring with the keyword descriptions - this was a straight copy/paste from the Figure.add_axes docstring, and then added the word "inset".
Updated the what's new entry (and the PR title and OP) to reflect that we're not going via Figure.add_axes.

rcomer · 2022-03-31T09:29:59Z

lib/matplotlib/tests/test_axes.py

@@ -6614,6 +6614,30 @@ def test_zoom_inset():
        axin1.get_position().get_points(), xx, rtol=1e-4)


+def test_inset_polar():
+    from matplotlib.projections.polar import PolarAxes


I imported the class within the test as I noticed another test in this module does that. If that's not necessary, then I think we could parametrize these three tests into one.

I do not see any reason to do this, I think pulling all of the imports to the top is OK.

I moved the imports to the top, but in the end couldn't convince myself it was worth parametrizing the two small tests that are still the same: since they're so small there isn't much repetition going on and I suspect readability is better as they are than with a parametrized version.

lib/matplotlib/tests/test_axes.py

tacaswell

I am 👍 with this going in as-is.

Moving to the mpl20 style would be good as would refactoring the test, but neither is worth holding up the PR over.

rcomer · 2022-04-04T19:09:31Z

Thanks @tacaswell, I am happy to follow those up tomorrow when I am back at my keyboard. Should I also squash the commits down to one?

tacaswell · 2022-04-04T19:16:48Z

Should I also squash the commits down to one?

Yes please (and if you replace the image CI without squashing CI will fail).

doc/users/next_whats_new/inset_axes_improvements.rst

lib/matplotlib/axes/_axes.py

lib/matplotlib/tests/test_axes.py

lib/matplotlib/axes/_axes.py

rcomer · 2022-04-07T12:00:36Z

Thanks All for your guidance!

rcomer changed the title ~~Use fig.add_axes within Axes.inset_axes~~ Use Figure.add_axes within Axes.inset_axes Mar 5, 2022

rcomer mentioned this pull request Mar 6, 2022

[Bug]: inset_axes position same as parent axes position. Breaks indicate_axes_zoom #22606

Closed

rcomer closed this Mar 6, 2022

rcomer mentioned this pull request Mar 9, 2022

[ENH]: enable passing of projection keyword to Axes.inset_axes #22630

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rcomer reopened this Mar 18, 2022

rcomer marked this pull request as draft March 18, 2022 16:12

rcomer closed this Mar 25, 2022

rcomer reopened this Mar 31, 2022

rcomer changed the title ~~Use Figure.add_axes within Axes.inset_axes~~ Axes.inset_axes: enable Axes subclass creation Mar 31, 2022

rcomer commented Mar 31, 2022

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rcomer marked this pull request as ready for review March 31, 2022 09:33

jklymak reviewed Mar 31, 2022

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rcomer force-pushed the inset-add_axes branch from f4d0101 to 4526225 Compare March 31, 2022 17:01

tacaswell added this to the v3.6.0 milestone Apr 1, 2022

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enable Axes subclass creation by Axes.inset_axes

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rcomer force-pushed the inset-add_axes branch from bcdaaf3 to 80e672e Compare April 5, 2022 10:47

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timhoffm merged commit 9caa261 into matplotlib:main Apr 7, 2022

rcomer deleted the inset-add_axes branch April 7, 2022 15:14

rcomer added the New feature label Jul 3, 2023

rcomer mentioned this pull request Dec 17, 2024

Propagate Axes class and kwargs for twinx and twiny #29325

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Axes.inset_axes: enable Axes subclass creation #22608

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