I need to create a linear color map with a color for "errors"

Question

I need to create a color map that behaves linearly between 0 and 1 on a grey scale.
Then I also want that any number outside the range [0,1] is drown red.

Would it be possible?

Asked By: Aslan986

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Source

Answer 1

You can take one of the existing black-white colormaps, and set its extremes to red. under and over set the color for values under or over the normalized bounds. bad is for color values that are NaN or infinity.

A copy() is needed to prevent changing matplotlib’s own copy of the colormap. When applying the colormap, it should go together with either explicitly setting vmin=0 and vmax=1, or using a norm.

To show the extremes in a colorbar, the extend= parameter can be used.

Here is an example, using the y-value for coloring.

import matplotlib.pyplot as plt
import numpy as np

my_cmap = plt.get_cmap('binary_r').copy()
my_cmap.set_extremes(bad='r', under='r', over='r')
np.random.seed(112358)
y = np.random.randn(200).cumsum() / 10
plt.scatter(x=np.arange(200), y=y, c=y, cmap=my_cmap, vmin=0, vmax=1)
plt.colorbar(extend='both')
plt.tight_layout()
plt.show()

Answered By: JohanC

I need to create a linear color map with a color for "errors"

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