Scientific notation colorbar in matplotlib

Question

I am trying to put a colorbar to my image using matplotlib. The issue comes when I try to force the ticklabels to be written in scientific notation. How can I force the scie

Answer 1

You could use colorbar's format parameter:

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.ticker as ticker

img = np.random.randn(300,300)
myplot = plt.imshow(img)

def fmt(x, pos):
    a, b = '{:.2e}'.format(x).split('e')
    b = int(b)
    return r'${} \times 10^{{{}}}$'.format(a, b)

plt.colorbar(myplot, format=ticker.FuncFormatter(fmt))
plt.show()

Answer 2

You can specify the format of the colorbar ticks as follows:

pl.colorbar(myplot, format='%.0e')

Answer 3

There is a more straightforward (but less customizable) way to get scientific notation in a ColorBar without the %.0e formatting.

Create your ColorBar:

cbar = plt.colorbar()

And call the formatter:

cbar.formatter.set_powerlimits((0, 0))

This will make the ColorBar use scientific notation. See the example figure below to see how the ColorBar will look.