如何使用 matplotlib plot 0/1 数组

Question

I'm given an input of 1/0 matrix. And i want to plot it to look like that: example

The thing is that i have to color all the zeros in blue. but when given a matrix of only ones it also turns into blue. is there a way to make the color "stick" with a specific number?

the code i've used:

cmap = ListedColormap(['b', 'g'])  
matrix=np.array(matrix,dtype=np.uint8) 
plt.imshow(matrix,cmap=cmap)

Answer 1

You could specify the default number of entries in the colormap using the ListedColormap method as you thought, just set the optional argument N = 2 . Also, define the minimum and maximum values for your data in the imshow method with vmin and vmax .

import matplotlib.pyplot as plt
from matplotlib.colors import ListedColormap
import numpy as np

# Random matrix

data_ones = np.random.randint(1, 2, size=(8, 8))
data_both = np.random.randint(0, 2, size=(8, 8))

# Define colormap

cmapmine = ListedColormap(['b', 'w'], N=2)

# Plot matrix

fig, (ax1, ax2) = plt.subplots(1, 2)
ax1.imshow(data_ones, cmap=cmapmine, vmin=0, vmax=1)
ax1.set_title('Ones')
ax2.imshow(data_both, cmap=cmapmine, vmin=0, vmax=1)
ax2.set_title('Zeros and Ones')
plt.show()

Which plots: