Set Matplotlib Colorbar Size to Match Graph

Set Matplotlib colorbar size to match graph

You can do this easily with a matplotlib AxisDivider.

The example from the linked page also works without using subplots:

import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable
import numpy as np
    
plt.figure()
ax = plt.gca()
im = ax.imshow(np.arange(100).reshape((10,10)))
    
# create an axes on the right side of ax. The width of cax will be 5%
# of ax and the padding between cax and ax will be fixed at 0.05 inch.
divider = make_axes_locatable(ax)
cax = divider.append_axes("right", size="5%", pad=0.05)
   
plt.colorbar(im, cax=cax)

Matplotlib: same height for colorbar as for plot

You can do this using make_axes_locatable:

import numpy
import matplotlib.pyplot as plt
import matplotlib.mlab as mlab
from mpl_toolkits.axes_grid1 import make_axes_locatable

#Generate data
delta = 0.025

x = numpy.arange(-5.0, 5.0, delta)
y = numpy.arange(-5.0, 5.0, delta)

X, Y = numpy.meshgrid(x, y)

Z1 = mlab.bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
Z2 = mlab.bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
# difference of Gaussians
Z = 10.0 * (Z2 - Z1)

#Plot
fig = plt.figure()
ax1 = fig.add_subplot(1, 1, 1,  aspect='equal')

PC = ax1.pcolor(X, Y, Z)
CF = ax1.contour(X, Y, Z, 50, colors = "black")

plt.xlim(-4.0, 4.0)
plt.ylim(-2.0, 2.0)

divider = make_axes_locatable(ax1)
cax1 = divider.append_axes("right", size="5%", pad=0.05)

cbar = plt.colorbar(PC, cax = cax1)
cbar.add_lines(CF)

plt.show()

Adjust the size of the colorbar to the size of a graph

Because you fixed the aspect ratio of the subplots to be 1, the subplots don't adjust to the figure's size, but the colorbar does. If you would not do that, the subplots would be as tall as the colorbar (but no more quadratic, of course...).

In turn you could simply define a figure size, which fits to the needed aspect ratio of three quadratic plots plus one colorbar, e.g.:

fig = plt.figure(figsize=(12, 3))

How to set Matplotlib colorbar height for image with aspect ratio 1

I finally found a solution here:

import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1.inset_locator import inset_axes

...

fig, ax = plt.subplots(1, 1)
im = ax.imshow(data, aspect = aspectRatio)
axins = inset_axes(ax, width = "5%", height = "100%", loc = 'lower left',
                   bbox_to_anchor = (1.02, 0., 1, 1), bbox_transform = ax.transAxes,
                   borderpad = 0)
fig.colorbar(im, cax = axins)

... where data is your array of values and 1.02 is the padding between the figure and the colorbar.

This creates colorbars with perfect height, regardless of the aspect ratio. No fiddling with magic numbers or anything of that sort.

How to set the ticks in matplotlib colorbar to be at the minimum and maximum value

Colorbars are my bane. This problem is relatively simple yet it took me a few minutes.

Add this line to the end of your code:

cbar.set_ticks(np.arange(0, 21, 5)) # 21 to guarantee 20 is included.

To get this:

Figure size changes with colorbar

Turns out, the solution to this problem is the keyword aspect, which needs to be set to auto. So:

image=sub.matshow(arr,origin='low',cmap=cm,vmin=vmin,vmax=vmax,extent=[-10.92,10.92,-10.92,10.92],interpolation='bilinear', aspect='auto')

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