Bug report

Bug summary

QuadMesh.get_clim() is documented as:

Return the values (min, max) that are mapped to the colormap limits.

Without vmin or vmax arguments to pcolormesh, this returns the data minimal and maximal values. However in the presence of only one of vmin or vmax, a change occurred between 3.2.2 and 3.3.0rc1. In 3.3.0rc1 it returns the input vmin and vmax, though only one of them was specified. The provided examples also happens (with slight output changes) for setting vmax instead of vmin.

Code for reproduction

import numpy as np
import matplotlib.pyplot as plt

dx, dy = 0.15, 0.05
y, x = np.mgrid[slice(-3, 3 + dy, dy),
                slice(-3, 3 + dx, dx)]
z = (1 - x / 2. + x ** 5 + y ** 3) * np.exp(-x ** 2 - y ** 2)
z = z[:-1, :-1]

f, ax = plt.subplots(1,1)
ax.pcolormesh(x, y, z, vmin=0)
ax.axis([x.min(), x.max(), y.min(), y.max()])
for mesh in ax.collections:
    print(mesh.get_clim())

Actual outcome

# 3.3.0rc1
(0.0, None)

Expected outcome

# 3.2.2
(0.0, 1.0510083319982622)

Matplotlib version

• Operating system: MacOSX
• Matplotlib version: 3.3.0rc1
• Matplotlib backend (print(matplotlib.get_backend())): MacOSX
• Python version: 3.8.3

Installed using pip