Issue with colorbar and imshow with gridspec

Question

I wanted to plot 2 imshow on a figure, but I only want the sub figure on the right to have the colorbar at the bottom of its plot.

import matplotlib.pyplot as plt
import numpy as np
from matplotlib.gridspec import GridSpec

cm = 1/2.54
fig = plt.figure()
fig.set_size_inches(21*cm,29.7*cm)
gs = GridSpec(1,2,figure=fig)

data1 = np.random.rand(100,1000)
data2 = np.random.rand(100,1000)

ax_left = fig.add_subplot(gs[:,0])
img_left = ax_left.imshow(data1, aspect='auto')

ax_right = fig.add_subplot(gs[:,1])
img_right = ax_right.imshow(data2, aspect='auto')

fig.colorbar(img_right,ax = [ax_right], location='bottom')

plt.show()

As you can see the 2 imshow are not the same size (I think because of the colorbar). Do you have any ideas to have the same figure but with the right plot with the same height as the left one (and keep the colorbar for the right imshow).

Answer 1

One way would be to add a second row to you grid and draw the colorbar in the bottom right grid using cax as kwarg:

import matplotlib.pyplot as plt
import numpy as np
from matplotlib.gridspec import GridSpec

cm = 1/2.54
fig = plt.figure()
fig.set_size_inches(21*cm,29.7*cm)
gs = GridSpec(2,2,figure=fig, hspace=0.1, height_ratios=[20, 1]) # adjust hspace and height_ratios to your liking

data1 = np.random.rand(100,1000)
data2 = np.random.rand(100,1000)

ax_left = fig.add_subplot(gs[0,0])
img_left = ax_left.imshow(data1, aspect='auto')

ax_right = fig.add_subplot(gs[0,1])
img_right = ax_right.imshow(data2, aspect='auto')

ax_cb = fig.add_subplot(gs[1,1])
fig.colorbar(img_right, cax=ax_cb, orientation='horizontal')

plt.show()

Output:

When you use colorbar, the height of the figure is different from the same figure without colorbar, because mpl makes the colorbar AND the graph fit on the same subplot.