从散点图中的调色板中选择两种颜色

Question

I am trying to make scatter plot in python using viridis palette with only two values. I really like the purple, but the yellow is bearly visible. is it possible to choose middle value (blue) and purple?

x_test = [1, 2, 3, 4]
y_test = [1, 2, 3, 4]
c_test = [0, 1, 0, 1]

plt.scatter(x = x_test, y = y_test, c = c_test,  alpha=1, cmap='viridis')

and it produce two colors - yellow and purple. The first one is not visible.

Answer 1

You can create your custom colormap with only 2 colors:

Code:

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


x_test = [1, 2, 3, 4]
y_test = [1, 2, 3, 4]
c_test = [0, 1, 0, 1]

mycmap = colors.ListedColormap(['purple', 'blue'])

plt.scatter(x = x_test, y = y_test, c = c_test,  alpha=1, cmap=mycmap, s=100)

Plot: