Matplotlib Contour Plot

Contour plots (sometimes called 'horizontal plots') are a method to display a three-dimensional surface on a two-dimensional plane. It draws two predicted variables X Y on the y-axis and the response variable Z of the contour. These contours are sometimes called z-slices or isoresponses.

Contour plots are very useful if you want to see how Z changes with the two input X and Y, for example, Z = f(X, Y). The contour lines or isoclines of a two-variable function are curves where the function has a constant value.

The independent variables x and y are usually limited to a regular grid called meshgrid. numpy.meshgrid creates a rectangular grid using the x value array and y value array.

The Matplotlib API includes the contour() and contourf() functions for drawing outlines and filled contours separately. Both functions require three parameters x, y, and z.

# Filename : example.py
# Copyright :　2020 By w3codebox
# Author by: www.oldtoolbag.com
# Date :　2020-08-08
import numpy as np
　import matplotlib.pyplot as plt
　xlist = np.linspace(-3.0,　3.0,　100)
　ylist = np.linspace(-3.0,　3.0,　100)
　X, Y = np.meshgrid(xlist, ylist)
　Z = np.sqrt(X**2　+　Y**2)
　fig, ax = plt.subplots(1,1)
　cp = ax.contourf(X, Y, Z)
　fig.colorbar(cp)  # Add a colorbar to a plot
　ax.set_title('Matplotlib Contour Plot')
　#ax.set_xlabel('x (cm)')
　ax.set_ylabel('y (cm)')
　plt.show()

Execute the above example code to get the following result -