Plot Contourf and Log Color Scale in Matplotlib

To plot contourf and log scale in Matplotlib, we can take the following steps −

• Set the figure size and adjust the padding between and around the subplots.
• Initialize a variable,N, for number of sample data.
• Create x, y, X, Y, Z1, Z2 and z data points using numpy.
• Create a figure and a set of subplots.
• Plot contours using contourf() method.
• Create a colorbar for a scalar mappable instance.
• To display the figure, use show() method.

Example

import matplotlib.pyplot as plt
import numpy as np
from numpy import ma
from matplotlib import ticker, cm

plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

N = 100
x = np.linspace(-3.0, 3.0, N)
y = np.linspace(-2.0, 2.0, N)

X, Y = np.meshgrid(x, y)

Z1 = np.exp(-X**2 - Y**2)
Z2 = np.exp(-(X * 10)**2 - (Y * 10)**2)

z = Z1 + 50 * Z2
z[:5, :5] = -1
z = ma.masked_where(z <= 0, z)
fig, ax = plt.subplots()

cs = ax.contourf(X, Y, z, locator=ticker.LogLocator(), cmap=cm.PuBu_r)
cbar = fig.colorbar(cs)

plt.show()

Output