how to extract a subset of a colormap as a new colormap in matplotlib?

Question

I would like to use a colormap from matplotlib e.g. CMRmap. But I don\'t want to use the \"black\" color at the beginning and the \"white\" color at the end. I\'m interested

Answer 1

Here is an adaptation of a previous answer which embeds the plotting function:

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

################### Function to truncate color map ###################
def truncate_colormap(cmapIn='jet', minval=0.0, maxval=1.0, n=100):
    '''truncate_colormap(cmapIn='jet', minval=0.0, maxval=1.0, n=100)'''    
    cmapIn = plt.get_cmap(cmapIn)

    new_cmap = colors.LinearSegmentedColormap.from_list(
        'trunc({n},{a:.2f},{b:.2f})'.format(n=cmapIn.name, a=minval, b=maxval),
        cmapIn(np.linspace(minval, maxval, n)))

    arr = np.linspace(0, 50, 100).reshape((10, 10))
    fig, ax = plt.subplots(ncols=2)
    ax[0].imshow(arr, interpolation='nearest', cmap=cmapIn)
    ax[1].imshow(arr, interpolation='nearest', cmap=new_cmap)
    plt.show()

    return new_cmap

cmap_mod = truncate_colormap(minval=.2, maxval=.8)  # calls function to truncate colormap

Having a compact function with the plotting embedded is helpful if you need to call the function more than once.