facecolors in plot_surface matplotlib

Question

I want to reproduce this example: https://matplotlib.org/3.3.1/gallery/mplot3d/surface3d_3.html#sphx-glr-gallery-mplot3d-surface3d-3-py but with different colors.

the original code is:

import matplotlib.pyplot as plt
from matplotlib.ticker import LinearLocator
import numpy as np


fig = plt.figure()
ax = fig.gca(projection='3d')

# Make data.
X = np.arange(-5, 5, 0.25)
xlen = len(X)
Y = np.arange(-5, 5, 0.25)
ylen = len(Y)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)

# Create an empty array of strings with the same shape as the meshgrid, and
# populate it with two colors in a checkerboard pattern.
colortuple = ('y', 'b')
colors = np.empty(X.shape, dtype=str)
for y in range(ylen):
    for x in range(xlen):
        colors[x, y] = colortuple[(x + y) % len(colortuple)]

# Plot the surface with face colors taken from the array we made.
surf = ax.plot_surface(X, Y, Z, facecolors=colors, linewidth=0)

# Customize the z axis.
ax.set_zlim(-1, 1)
ax.zaxis.set_major_locator(LinearLocator(6))

plt.show()

when i change "colortuple =('y', 'b')" to "colortuple =('#ff7f0e', '#2ca02c') i am having this error:

  File "<ipython-input-41-a355b1dad171>", line 1, in <module>
    runfile('C:/Users/camrane/Downloads/dflt_style_changes-1.py', wdir='C:/Users/camrane/Downloads')

  File "C:\ProgramData\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 705, in runfile
    execfile(filename, namespace)

  File "C:\ProgramData\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users/camrane/Downloads/dflt_style_changes-1.py", line 27, in <module>
    surf = ax.plot_surface(X, Y, Z, facecolors=colors, linewidth=0)

  File "C:\ProgramData\Anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line 1740, in plot_surface
    colset = self._shade_colors(colset, normals)

  File "C:\ProgramData\Anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line 1790, in _shade_colors
    color = mcolors.to_rgba_array(color)

  File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\colors.py", line 267, in to_rgba_array
    result[i] = to_rgba(cc, alpha)

  File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\colors.py", line 168, in to_rgba
    rgba = _to_rgba_no_colorcycle(c, alpha)

  File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\colors.py", line 212, in _to_rgba_no_colorcycle
    raise ValueError("Invalid RGBA argument: {!r}".format(orig_c))

ValueError: Invalid RGBA argument: '#'

)"

and when it is to "colortuple =('gray', 'orange') i have this error

  File "<ipython-input-42-a355b1dad171>", line 1, in <module>
    runfile('C:/Users/camrane/Downloads/dflt_style_changes-1.py', wdir='C:/Users/camrane/Downloads')

  File "C:\ProgramData\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 705, in runfile
    execfile(filename, namespace)

  File "C:\ProgramData\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 102, in execfile
    exec(compile(f.read(), filename, 'exec'), namespace)

  File "C:/Users/camrane/Downloads/dflt_style_changes-1.py", line 27, in <module>
    surf = ax.plot_surface(X, Y, Z, facecolors=colors, linewidth=0)

  File "C:\ProgramData\Anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line 1740, in plot_surface
    colset = self._shade_colors(colset, normals)

  File "C:\ProgramData\Anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py", line 1790, in _shade_colors
    color = mcolors.to_rgba_array(color)

  File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\colors.py", line 267, in to_rgba_array
    result[i] = to_rgba(cc, alpha)

  File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\colors.py", line 168, in to_rgba
    rgba = _to_rgba_no_colorcycle(c, alpha)

  File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\colors.py", line 212, in _to_rgba_no_colorcycle
    raise ValueError("Invalid RGBA argument: {!r}".format(orig_c))

ValueError: Invalid RGBA argument: 'o'

It is like the code accpets only basic colors.

Thanks

Answer 1

Interesting problem. This is due to the way the colors array is created in the example.

colortuple = ('y', 'b')
colors = np.empty(X.shape, dtype=str)
for y in range(ylen):
    for x in range(xlen):
        colors[x, y] = colortuple[(x + y) % len(colortuple)]

because the colors array is declared with dtype=str, it only accepts only 1 char per cell, and the colors that you are trying to use are truncated.

From this answer, you can initialize the array with a larger size to circumvent this issue colors = np.empty(X.shape, dtype='U50')

import matplotlib.pyplot as plt
from matplotlib.ticker import LinearLocator
import numpy as np


fig = plt.figure()
ax = fig.gca(projection='3d')

# Make data.
X = np.arange(-5, 5, 0.25)
xlen = len(X)
Y = np.arange(-5, 5, 0.25)
ylen = len(Y)
X, Y = np.meshgrid(X, Y)
R = np.sqrt(X**2 + Y**2)
Z = np.sin(R)

# Create an empty array of strings with the same shape as the meshgrid, and
# populate it with two colors in a checkerboard pattern.
colortuple = ('xkcd:blue with a hint of purple', '#ff7f0e', 'orange')
colors = np.empty(X.shape, dtype='U50')
for y in range(ylen):
    for x in range(xlen):
        colors[x, y] = colortuple[(x + y) % len(colortuple)]

# Plot the surface with face colors taken from the array we made.
surf = ax.plot_surface(X, Y, Z, facecolors=colors, linewidth=0)

# Customize the z axis.
ax.set_zlim(-1, 1)
ax.zaxis.set_major_locator(LinearLocator(6))

plt.show()