Add axis to colorbar in python matplotlib

Question

I am trying to produce a figure like the following in python:

I am done with most part of it and currently based on what I want it looks like this:

And my code is:

plt.scatter(x,y,marker="h",s=100,c=color)
plt.xscale('log')
plt.yscale('log')
plt.xlim([1, 10**3])
plt.ylim([1, 10**3])
plt.colorbar()
plt.show()

Is there any way to make the current colorbar look like the one on top? So to make it smaller and add axis to it?

Any help would be much appreciated.

Answer 1

The key here is the cax kwarg to colorbar. You'll need to create an inset axes, and then use that axes for the colorbar.

As an example:

import numpy as np
import matplotlib.pyplot as plt

npoints = 1000
x, y = np.random.normal(10, 2, (2, npoints))

fig, ax = plt.subplots()
artist = ax.hexbin(x, y, gridsize=20, cmap='gray_r', edgecolor='white')

# Create the inset axes and use it for the colorbar.
cax = fig.add_axes([0.8, 0.15, 0.05, 0.3])
cbar = fig.colorbar(artist, cax=cax)

plt.show()

If you wanted to get fancy and more precisely match things (Note: I'm using hexbin here, which doesn't support log axes, so I'm leaving that part out.)

import numpy as np
import matplotlib.pyplot as plt

npoints = 1000
x, y = np.random.normal(10, 2, (2, npoints))

fig, ax = plt.subplots()
artist = ax.hexbin(x, y, gridsize=20, cmap='gray_r', edgecolor='white')

cax = fig.add_axes([0.8, 0.15, 0.05, 0.3])
cbar = fig.colorbar(artist, cax=cax)

ax.spines['right'].set(visible=False)
ax.spines['top'].set(visible=False)
ax.tick_params(top=False, right=False)

cbar.set_ticks([5, 10, 15])
cbar.ax.set_title('Bin Counts', ha='left', x=0)
cbar.ax.tick_params(axis='y', color='white', left=True, right=True,
                    length=5, width=1.5)
cbar.outline.remove()

plt.show()