Matplotlib for Python Developers - Second Edition

Adding a trendline over a scatter plot

Multiple plot types can be overlaid on top of each other. For example, we can add a trendline over a scatter plot. The following is an example of adding a trendline to 10 y coordinates with slight deviations from a linear relationship with the x coordinates:

import numpy as npimport matplotlib.pyplot as plt# Generate thnp.random.seed(100)x = list(range(10))y = x+np.random.rand(10)-0.5# Calculate the slope and y-intercept of the trendlinefit = np.polyfit(x,y,1)# Add the trendlineyfit = [n*fit[0] for n in x]+fit[1]plt.scatter(x,y)plt.plot(yfit,'black')plt.show()

We can observe from the following plot that the trendline overlays the upward sloping dots: