[Matplotlib-users] Color Bar Limits

Hi all,

I’m plotting some scatter points colored by a third variable, but want to use a limited subset of a colormap. In the example below, the color axis data ranges from 0-4, but I want to not use the red portion of the bar. Doing the first part is just accomplished by setting the vmin/vmax. But when I plot a color bar I don’t want to show the colors and values for anything below zero. Other than just white-boxing that part of the bar I’m not sure how to do it. I tried a suggestion of setting the limit properties of the bar axis attribute, but that results in the bar getting shrunk and shifted (a very weird behavior). Any ideas?

Thank you,

John Leeman

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(100)
y = np.random.rand(100)
z = 4 * np.random.rand(100)

color_map = plt.get_cmap('rainbow_r')

fig = plt.figure(figsize=(12,9))
ax1 = plt.subplot(111)
sc = ax1.scatter(x, y, c=z, s=50, cmap=color_map, vmin=-1, vmax=4)

position=fig.add_axes([0.37, 0.16, 0.5, 0.02])
cb = fig.colorbar(sc, cax=position, orientation='horizontal', drawedges=False)
cb.set_label('Z-Colors’, fontsize=14)

# I tried this after talking with Ben Root, but it
# results in some odd behavior
# cb.ax.set_xlim(0,4)

plt.show()