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[Bug]: colorbar for matshow taller than plot unless using fignum=0 #22972
Description
Bug summary
When using plt.colorbar along with plt.matshow, the colorbar is taller than the plot. If I use plt.matshow(A, fig=0), then it is the same height as the plot.
Code for reproduction
# Basically https://matplotlib.org/stable/gallery/images_contours_and_fields/matshow.html#sphx-glr-gallery-images-contours-and-fields-matshow-py with a colorbar added
import matplotlib.pyplot as plt
import numpy as np
# a 2D array with linearly increasing values on the diagonal
a = np.diag(range(15))
plt.matshow(a) # this triggers the bug
# plt.matshow(a, fignum=None) # this too
# plt.matshow(a, fignum=1) # this too
# plt.matshow(a, fignum=False) # this triggers the expected outcome
# plt.matshow(a, fignum=0) # this too
plt.colorbar()
plt.show()Actual outcome
Expected outcome
Additional information
No response
Operating system
Ubuntu 20.04
Matplotlib Version
3.5.2
Matplotlib Backend
QtAgg
Python version
Python 3.10.4
Jupyter version
none involved
Installation
conda
Activity
jklymak commentedon May 4, 2022
I don;'t know what your fig=0 etc are doing, but the general behaviour is expected that fixed-aspect axes can have colorbars that are too tall (or too wide). Make the aspect ratio of the figure such that the blank space is horizontal instead of vertical. Please see: https://matplotlib.org/3.5.0/gallery/subplots_axes_and_figures/colorbar_placement.html#colorbars-with-fixed-aspect-ratio-axes. I'll close this here, but feel free to discuss at https://discourse.matplotlib.org
[-][Bug]: colorbar for `matshow` taller than plot unless using `fig=0`[/-][+][Bug]: colorbar for `matshow` taller than plot unless using `fignum=0`[/+]phil-blain commentedon May 4, 2022
Thanks for the reply.
For the record here is the description of the
fignumargument from the doc:Since in my example no figure exist beforehand, according to the doc I would expect
fignum=None( the default),fignum=1,fignum=0andfignum=Falseto all behave the same...anntzer commentedon Nov 1, 2023
Note that even fignum=0/False won't work for "wide" matrices, e.g.
matshow(rand(3, 8), fignum=0); colorbar()still results in a too-tall colorbar. In general I agree with the comment above that one cannot rely on matshow getting the right colorbar size automatically.(I also agree that the behavior of matshow wrt. fignum is confusing -- see #27244.)