How to customize the Python contourf color map-CodePudding

The following contourf plots were created in Python as well as in Mathcad. The colormap for both plots is 'Greens'. I'd like my plot to look like Mathcad's where low values are represented by black (or very dark green). In order to achieve this, I used the hint given

The code is as follows:

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

r = np.linspace(0, 1.5, 50)
p = np.linspace(0, 2*np.pi, 50)
R, P = np.meshgrid(r, p)
z1 = ((R**2 - 1)**2)
# Express the mesh in the cartesian system.
x1, y1 = R*np.cos(P), R*np.sin(P)

fig = plt.Figure()
ax = plt.axes()
levels = np.linspace(z1.min(), z1.max(), 100)
cmap = mpl.cm.Greens_r(np.linspace(0,1,100))
cmap = mpl.colors.ListedColormap(cmap[:,:70])
cont = ax.contourf(x1, y1, z1, cmap=cmap,  vmin=z1.min(), vmax=z1.max(), levels=levels)
plt.colorbar(cont)
plt.title('Matplotlib')
plt.show()

CodePudding user response：

The Greens colormap goes from Black to Green to White in matplotlib. You only want the portion going from Black to Green (also, the green you want is more vivid than in the matplotlib colormap). There are several options available to achieve this (e.g. you could truncate the colormap using something like the answer