Colorbar for matplotlib plot_surface command

Question

I have modified the mplot3d example code for my application with Paul's help. The code reads:

from mpl_toolkits.mplot3d import Axes3D import matplotlib.pyplot as plt import numpy as np  fig = plt.figure() ax = fig.add_subplot(111, projection='3d')  u = np.linspace(0, 2 * np.pi, 100) v = np.linspace(0, np.pi, 100)  x = 10 * np.outer(np.cos(u), np.sin(v)) y = 10 * np.outer(np.sin(u), np.sin(v)) z = 10 * np.outer(np.ones(np.size(u)), np.cos(v)) z1 = z * np.cos(0.5*x)  N = z1 / z1.max()  # normalize 0..1 surf = ax.plot_surface(x, y, z, rstride=1, cstride=1, facecolors=cm.jet(N), linewidth=0, antialiased=False, shade=False)  fig.colorbar(surf, shrink=0.5, aspect=5) plt.show() 

The code works great to plot the surface. But when I try to add a colorbar to the above plot, I get the following error:

Traceback (most recent call last):   File "<ipython console>", line 1, in <module>   File "C:\Python26\lib\site-packages\spyderlib\widgets\externalshell\startup.py", line 122, in runfile     execfile(filename, glbs)  File "C:\Documents and Settings\mramacha\My Documents\Python\Candela\test.py", line 22, in <module>     fig.colorbar(surf, shrink=0.5, aspect=5)   File "C:\Python26\lib\site-packages\matplotlib\figure.py", line 1104, in colorbar     cb = cbar.Colorbar(cax, mappable, **kw)   File "C:\Python26\lib\site-packages\matplotlib\colorbar.py", line 706, in __init__     mappable.autoscale_None() # Ensure mappable.norm.vmin, vmax   File "C:\Python26\lib\site-packages\matplotlib\cm.py", line 261, in autoscale_None     raise TypeError('You must first set_array for mappable') TypeError: You must first set_array for mappable 

I would be so grateful if someone is able to guide me with this.

Prabhu

Answer 1

You can use a proxy mappable object since your surface array is not mapped. The mappable simply converts the values of any array to RGB colors defined by a colormap.

In your case you want to do this with the z1 array:

import matplotlib.cm as cm m = cm.ScalarMappable(cmap=cm.jet) m.set_array(z1) plt.colorbar(m)