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FIX: make add_lines work with new colorbar#12461

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dstansby merged 3 commits intomatplotlib:masterfrom
jklymak:fix-cbar-addlines
Oct 14, 2018
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FIX: make add_lines work with new colorbar#12461
dstansby merged 3 commits intomatplotlib:masterfrom
jklymak:fix-cbar-addlines

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@jklymak jklymak commented Oct 9, 2018 •
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PR Summary

Closes #12458

See below for a less pathological example...

cbar.add_lines was not operational after new colorbar changes in 3.0.0.

import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np

fig = plt.figure()
ax = fig.add_axes([0.05, 0.8, 0.9, 0.15])
cmap = mpl.cm.cool
norm = mpl.colors.Normalize(vmin=-4, vmax=4)
levels = (-1.0, 1.0, 2.0, 3.0)

cb = mpl.colorbar.ColorbarBase(ax, cmap=cmap, norm=norm)
colors_bg = np.tile(list((1.0, 1.0, 1.0, 1.0)), (len(levels), 1))
cb.add_lines(levels=levels, colors=colors_bg, linewidths=1)

Before

cbarold

After

cbarnew

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
X = np.random.rand(10, 10)*10000
pcm = ax.pcolormesh(X)
# add 1000 to make colors visible...
cont = ax.contour(X+1000)
cb = fig.colorbar(pcm)
cb.add_lines(cont)
plt.show()

Before

before

After

new

PR Checklist

  • Has Pytest style unit tests
  • Code is Flake 8 compliant
  • New features are documented, with examples if plot related
  • Documentation is sphinx and numpydoc compliant
  • Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
  • Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

@jklymak jklymak changed the title FIX: make add_lines wortk with new colorbar FIX: make add_lines work with new colorbar Oct 9, 2018
@jklymak jklymak added this to the v3.0.x milestone Oct 9, 2018
@jklymak jklymak mentioned this pull request Oct 9, 2018
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@dstansby
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dstansby commented Oct 9, 2018

Huh, and here I am manually adding lines to the cbar axes with axhline! You learn a new bit of the API every day...

@jklymak
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jklymak commented Oct 9, 2018

Well, except the subclass Colorbar actually has a very different add_lines, so you need to call the cb.super().add_lines() to get this API. Hence, I doubt its tested, and this PR needs tests.

We could extend the API of cb.add_lines to check if the first argument is a list of levels instead of a ContourSet, but that entails a bunch of extra kwargs to pass down.

You must have been bit by the 3.0 change, i.e. the colorbar no longer has native co-ordinates from 0 to 1, but rather from vmin to vmax....

@jklymak jklymak mentioned this pull request Oct 9, 2018
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jklymak commented Oct 9, 2018

Grrr, test failures are real, with the lines slightly extended a bit further into the lhs of the axes. I don't think either version is "wrong", and the PDFs are the same, so I'll upload the new images for this one.

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jklymak commented Oct 9, 2018

Added new test image to test that the lines are added properly to a colorbar.

@jklymak jklymak added Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions. and removed status: work in progress labels Oct 9, 2018
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anntzer commented Oct 9, 2018

Based on @dstansby's comment, I guess (especially after #12380 gets merged :p) we could just rewrite the thing to use vlines()/hlines() instead?

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jklymak commented Oct 9, 2018

@anntzer are you proposing we do that here? I was just going for the minimal change to fix the code. If we want to make a 3.1 upgrade, I'd be all for that. Would appending the collection to self.lines be the same as appending all the hlines? If not, it'd also be an API change...

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anntzer commented Oct 9, 2018 •
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I think this can go in as is for now (well I didn't review it carefully, but looks fine).
After #12380 hlines() will create a LineCollection just like add_lines currently does so no API break then.

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jklymak commented Oct 9, 2018

?? #12380 is for stem. OTOH, I see thet ax.hlines indeed returns a line collection, so maybe just as well to use that? But for now, I still think we should do that as a new PR for 3.1...

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QuLogic commented Oct 9, 2018

I don't think either version is "wrong", and the PDFs are the same, so I'll upload the new images for this one.

I think the old one is wrong, actually. The LHS shows some mixing of the line and the colorbar below, whereas the new one goes right to the edge line.

@jklymak
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jklymak commented Oct 9, 2018

I don't think either version is "wrong", and the PDFs are the same, so I'll upload the new images for this one.

I think the old one is wrong, actually. The LHS shows some mixing of the line and the colorbar below, whereas the new one goes right to the edge line.

Yeah, I don't quite understand from the code why that is the case, however... Before the xaxis went from [0, 1], now it goes from [vmin, vmax], and this PR just redraws across those limits for both cases. Maybe something funky about axes that go from [0, 1]?

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anntzer commented Oct 9, 2018

Oh sorry yes I got PRs mixed up. I guess yes you may as well use hlines/vlines here then...

@dstansby dstansby merged commit fbd0fba into matplotlib:master Oct 14, 2018
meeseeksmachine pushed a commit to meeseeksmachine/matplotlib that referenced this pull request Oct 14, 2018
@dstansby
Backport PR matplotlib#12461: FIX: make add_lines work with new colorbar
3dde05b
@meeseeksmachine meeseeksmachine mentioned this pull request Oct 14, 2018
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QuLogic added a commit that referenced this pull request Oct 14, 2018
@QuLogic
Merge pull request #12527 from meeseeksmachine/auto-backport-of-pr-12…
b8e2e1b 
…461-on-v3.0.x

Backport PR #12461 on branch v3.0.x (FIX: make add_lines work with new colorbar)
@jklymak jklymak deleted the fix-cbar-addlines branch October 22, 2018 17:41
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@timhoffm timhoffm timhoffm approved these changes

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Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions.

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add_lines misses lines for matplotlib.colorbar.ColorbarBase

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@jklymak @dstansby @anntzer @QuLogic @timhoffm