plt.pcolormesh shape mismatch when shading='gouraud' #8422
Description
Bug report
Bug summary
When running plt.pcolormesh(X, Y, C, shading='flat'), if C.shape == (nrows, ncols), then if X and Y are 2-D arrays, their shapes must be either (nrows, ncols) or (nrows+1, ncols+1). If shading='gouraud', however, the latter results in an error. The code snippet below uses 1-D arrays for X and Y, but the same error occurs when they are the equivalent 2-D arrays.
Code for reproduction
import numpy as np
import matplotlib.pyplot as plt
x = np.arange(-4, 5)
y = np.arange(-6, 7)
xe = np.linspace(-4.5, 4.5, 10)
ye = np.linspace(-6.5, 6.5, 14)
c = np.exp(-0.5*0.125*(x.reshape(1, -1)**2 + y.reshape(-1, 1)**2))
plt.pcolormesh(xe, ye, c, shading='flat') # works
plt.pcolormesh(x, y, c, shading='gouraud') # works
plt.pcolormesh(xe, ye, c, shading='gouraud') # doesn't workActual outcome
Traceback (most recent call last):
File "<ipython-input-67-154f761638cd>", line 1, in <module>
plt.pcolormesh(xe, ye, c, shading='gouraud')
File "/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/pyplot.py", line 3245, in pcolormesh
ret = ax.pcolormesh(*args, **kwargs)
File "/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/__init__.py", line 1892, in inner
return func(ax, *args, **kwargs)
File "/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 5569, in pcolormesh
X, Y, C = self._pcolorargs('pcolormesh', *args, allmatch=allmatch)
File "/home/egranstedt/anaconda3/lib/python3.6/site-packages/matplotlib/axes/_axes.py", line 5187, in _pcolorargs
C.shape, Nx, Ny, funcname))
TypeError: Dimensions of C (13, 9) are incompatible with X (10) and/or Y (14); see help(pcolormesh)
Expected outcome
I expected pcolormesh would accept the same arrays for X and Y irrespective of the setting of the shading` keyword argument.
Matplotlib version
- The error occurs with Matplotlib version 2.0.0 in the python 3.6 interpreter on Linux (installed via anaconda), but also seems to exist in older versions of Matplotlib (e.g., 1.5.1)