Search for a colormap with similarities to CMRmap

Question

I'm looking for the following colormap in matplotlib, which I saw in a paper:

At first I thought it was a section of the CMRmap colormap.

cmap = plt.get_cmap('CMRmap')
new_cmap = truncate_colormap(cmap, 0.0, 0.75) #(https://stackoverflow.com/a/18926541/7559986)

However, the following came out when I extract a subset of it, which looks a bit different (especially the yellow):

Does anyone know how I get to the upper colormap?

Answer 1

The colormap you show looks like it's just an interpolation between black, blue, red and yellow. This would be created via

matplotlib.colors.LinearSegmentedColormap.from_list("", ["black", "blue", "red", "yellow"])

However, I would not recommend using such colormap. Instead use any of "viridis", "magma", "plasma" or "inferno". Those are perceptually uniform and hence do not create unwanted artifacts.

Below is a comparisson between the interpolated map and "magma". As you can see the interpolated map creates "rings", such that the viewer would surely misinterprete the shape that is plotted.

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

x = np.linspace(-2,2, 101)
X,Y = np.meshgrid(x,x)
Z = np.exp(-X**2-Y**2)

fig, (ax1, ax2) = plt.subplots(ncols=2)

im1 = ax1.imshow(Z, cmap="magma")


cmap = mcolors.LinearSegmentedColormap.from_list("", ["black", "blue", "red", "yellow"])
im2 = ax2.imshow(Z, cmap=cmap)

fig.colorbar(im1, ax=ax1, orientation="horizontal")
fig.colorbar(im2, ax=ax2, orientation="horizontal")

plt.show()

Further reading

• https://matplotlib.org/3.1.1/tutorials/colors/colormaps.html
• https://bids.github.io/colormap/ on why it's bad to use such non-uniform maps.