Assign Specific Values to Matplotlib graph

Question

I have two values in a numpy array. 0,1. I want to ensure 1 is always black and 0 is always grey when I graph the array.

How can I do this in matplotlib?

Thank you

Which kind of plot do you want to use? Please also read How to Ask. — ImportanceOfBeingErnest
– ImportanceOfBeingErnest, Commented Apr 6, 2017 at 12:31

ImportanceOfBeingErnest · Accepted Answer · 2017-04-06 12:37:34Z

3

Assuming that you want to plot an image plot (plt.imshow()), you can select a colormap like "gray_r" which has white as lowest and black as highest color, gray will be in the middle. If you now normalize the image plot to values between -1 and 1, the array's 0 value will correspond to the middle of the colormap (being gray) and 1 will correspond to the upper end of the colormap (being black).

import matplotlib.pyplot as plt
import numpy as np; np.random.seed(0)

a = np.random.randint(0,2, size=(12,25))

plt.imshow(a, cmap="gray_r", vmin=-1, vmax=1)

plt.show()

answered Apr 6, 2017 at 12:37

ImportanceOfBeingErnest

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