Description
Bug summary
When creating multiple Axes with boxplots, all on the same Figure, adding minor gridlines using minorticks_on() causes a traceback only if more than 1 Axes has boxplots on it.
Code for reproduction
from random import random
import matplotlib.pyplot as plt
if __name__ == "__main__":
fig, axes = plt.subplots(sharex=True, ncols=2, nrows=2)
def values():
return [random() for _ in range(9)]
for x in range(3):
"""
Code works as is, with commented lines not being run.
When I uncomment any of the below boxplot() calls, I am getting the error
mentioned in the bug report.
"""
# axes[0, 0].boxplot(values(), positions=[x])
# axes[0, 1].boxplot(values(), positions=[x])
# axes[1, 0].boxplot(values(), positions=[x])
axes[1, 1].boxplot(values(), positions=[x])
for ax in axes.flatten():
ax.grid(which="major", color="k", alpha=0.3)
ax.grid(which="minor", color="k", alpha=0.1, linestyle="--")
ax.minorticks_on()
plt.show()Actual outcome
When I run this code exactly as I've pasted into the code for repro box, I get a Figure with 4 Axes. Each of them has major and minor gridlines (expected/desired), and one of them contains a set of boxplots.
When I run this and attempt to create boxplots on a second Axes within the figure, I get the following traceback when the Figure is attempted to be rendered:
Traceback (most recent call last):
File "python3.9/site-packages/matplotlib/backend_bases.py", line 1226, in _on_timer
ret = func(*args, **kwargs)
File "python3.9/site-packages/matplotlib/backends/backend_macosx.py", line 68, in callback_func
callback()
File "python3.9/site-packages/matplotlib/backends/backend_macosx.py", line 88, in _draw_idle
self.draw()
File "python3.9/site-packages/matplotlib/backends/backend_macosx.py", line 50, in draw
super().draw()
File "ython3.9/site-packages/matplotlib/backends/backend_agg.py", line 400, in draw
self.figure.draw(self.renderer)
File "python3.9/site-packages/matplotlib/artist.py", line 95, in draw_wrapper
result = draw(artist, renderer, *args, **kwargs)
File "python3.9/site-packages/matplotlib/artist.py", line 72, in draw_wrapper
return draw(artist, renderer)
File "python3.9/site-packages/matplotlib/figure.py", line 3140, in draw
mimage._draw_list_compositing_images(
File "python3.9/site-packages/matplotlib/image.py", line 131, in _draw_list_compositing_images
a.draw(renderer)
File "python3.9/site-packages/matplotlib/artist.py", line 72, in draw_wrapper
return draw(artist, renderer)
File "python3.9/site-packages/matplotlib/axes/_base.py", line 3028, in draw
self._update_title_position(renderer)
File "python3.9/site-packages/matplotlib/axes/_base.py", line 2963, in _update_title_position
bb = ax.xaxis.get_tightbbox(renderer)
File "python3.9/site-packages/matplotlib/axis.py", line 1323, in get_tightbbox
ticks_to_draw = self._update_ticks()
File "python3.9/site-packages/matplotlib/axis.py", line 1270, in _update_ticks
minor_locs = self.get_minorticklocs()
File "python3.9/site-packages/matplotlib/axis.py", line 1489, in get_minorticklocs
minor_locs = np.asarray(self.minor.locator())
File "python3.9/site-packages/matplotlib/ticker.py", line 2955, in __call__
locs = np.arange(tmin, tmax, minorstep) + t0
ValueError: arange: cannot compute length`
In addition, the 3 commented out boxplot() calls can be made successfully without throwing this error at render-time if you don't call ax.minorticks_on(), however AFAIK this is the way to ensure the minor gridlines are shown.
Expected outcome
A Figure with 4 Axes, each of which containing a series of boxplots with major and minor gridlines drawn as well.
Additional information
Machine is a Mac with an Apple M1 CPU.
Operating system
OS/X
Matplotlib Version
3.7.1
Matplotlib Backend
MacOSX
Python version
3.9.6
Jupyter version
No response
Installation
pip