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[Bug]: SymLogNorm not working properly #22870

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oscargus opened this issue Apr 21, 2022 · 3 comments
Closed

[Bug]: SymLogNorm not working properly #22870

oscargus opened this issue Apr 21, 2022 · 3 comments
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topic: ticks axis labels

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@oscargus
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oscargus commented Apr 21, 2022 •
edited
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Bug summary

(It is, sort of, well known that this is broken, see e.g. #16398, but good to have a separate issue for it in case someone is tempted to give it a go.)
Here is an example for a colorbar, but a similar behavior is seen elsewhere:

matplotlib/tutorials/colors/colormapnorms.py

Lines 132 to 148 in a7b7260

N = 100
X, Y = np.mgrid[-3:3:complex(0, N), -2:2:complex(0, N)]
Z1 = np.exp(-X**2 - Y**2)
Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)
Z = (Z1 - Z2) * 2
fig, ax = plt.subplots(2, 1)
pcm = ax[0].pcolormesh(X, Y, Z,
norm=colors.SymLogNorm(linthresh=0.03, linscale=0.03,
vmin=-1.0, vmax=1.0, base=10),
cmap='RdBu_r', shading='auto')
fig.colorbar(pcm, ax=ax[0], extend='both')
pcm = ax[1].pcolormesh(X, Y, Z, cmap='RdBu_r', vmin=-np.max(Z), shading='auto')
fig.colorbar(pcm, ax=ax[1], extend='both')
plt.show()

gives

image

As seen, the top colorbar has a messed scale.

Code for reproduction

See above.

Actual outcome

Overlapping tick labels.

Expected outcome

Non-overlapping tick labels.

Additional information

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Operating system

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Matplotlib Version

Current main (pre-3.6.0)

Matplotlib Backend

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Python version

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Jupyter version

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Installation

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@jklymak
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jklymak commented Apr 21, 2022

I don't think this is a colorbar issue in particular. Don't you get the same with any symlognorm axis?

@oscargus
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You are probably right. Just saw it there. I'll edit appropriately.

@oscargus oscargus changed the title [Bug]: SymLogNorm not working with (at least) colorbar [Bug]: SymLogNorm not working properly Apr 21, 2022
@oscargus
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And then I found an issue searching for SymmetricalLogLocator instead (not sure where the actual error is, but in one of those most likely). #18757

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@jklymak @oscargus