[Bug]: Colorbar does not work for negative values with contour/contourf #21882
Description
Bug summary
The colorbar does not work with contour/contourf, if the data contains negative values AND zeros.
The error message is the following:
matplotlib/transforms.py:2663: RuntimeWarning: divide by zero encountered in double_scalars
y_scale = 1.0 / inh
matplotlib/transforms.py:2665: RuntimeWarning: invalid value encountered in double_scalars
[0.0 , y_scale, (-inb*y_scale)]
It does work for only negative (without zero), only positive (without zero), and mixed positive and negative values.
The colorbar also works with imshow regardless of the data.
Code for reproduction
import matplotlib.pyplot as plt
import numpy as np
# mixed positive and negative values work
data = np.arange(-5, 4).reshape((3,3))
fig, ax = plt.subplots()
im = ax.contourf(data)
cb = plt.colorbar(im)
# negative and zero does not work!
data = np.arange(-5, 4).reshape((3,3))
vmax = np.max(data)
data -= vmax
fig, ax = plt.subplots()
im = ax.contourf(data)
cb = plt.colorbar(im)Actual outcome
First example that works!
Second example that does not work!
Expected outcome
The same plot as the first example with a colorbar from 0 to -9, which is produced with matplotlib 3.4.3.
Additional information
No response
Operating system
No response
Matplotlib Version
3.5.0
Matplotlib Backend
No response
Python version
No response
Jupyter version
No response
Installation
No response