How to 'turn off' blurry effect of imshow() in matplotlib?

Question

I want to make a color plot of probabilities however imshow generates blurry values for points which have zero probability. How can I get rid of this blurry periphery around real grid points?

Example:

import numpy as np
import matplotlib.pyplot as plt

a=np.asarray([[  0.00000000e+00 , 1.05824446e-01 ,  2.05086136e-04,   0.00000000e+00],
[  1.05824446e-01 ,  3.15012305e-01  , 1.31255127e-01  , 1.05209188e-01],
 [  2.05086136e-04  , 1.31255127e-01 ,  0.00000000e+00 ,  0.00000000e+00],
 [  0.00000000e+00   ,1.05209188e-01  , 0.00000000e+00  , 0.00000000e+00]])
im=plt.imshow(a,extent=[0,4,0,4],origin='lower',alpha=1,aspect='auto')
plt.show()

Answer 1

By default (which is changed mpl 2.0), imshow interpolates the data (as you would want to do for an image). All you need to do is tell it to not interpolate:

im = plt.imshow(..., interpolation='none')

'nearest' will also work for what you want. See smoothing between pixels of imagesc\\imshow in matlab like the matplotlib imshow for examples of all of the kinds of interpolation.

doc

Answer 2

You may also use:

im = plt.imshow(..., interpolation='nearest')

This works especially well for discrete variables.