How to update a plot in Matplotlib?

In this article, let’s discuss how to update a plot in Matplotlib. Updating a plot simply means plotting the data, then clearing the existing plot, and then again plotting the updated data and all these steps are performed in a loop. 

Functions Used:

• canvas.draw(): It is used to update a figure that has been changed. It will redraw the current figure.
• canvas.flush_events(): It holds the GUI event till the UI events have been processed. This will run till the loop ends and values will be updated continuously.

Below is the implementation.

• Creating the data to plot using:

Python3

x = np.linspace(0, 10*np.pi, 100)
y = np.sin(x)

• Turn on interactive mode using:

Python3

plt.ion()

•  Now we will configure the plot (the ‘b-‘ indicates a blue line):

Python3

fig = plt.figure()
ax = fig.add_subplot(111)
line1, = ax.plot(x, y, 'b-')

• And finally, update in a loop:

Python3

for phase in np.linspace(0, 10*np.pi, 100):
    line1.set_ydata(np.sin(0.5 * x + phase))
    fig.canvas.draw()
    fig.canvas.flush_events()

Complete code.

Python3

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0, 10*np.pi, 100)
y = np.sin(x)

plt.ion()
fig = plt.figure()
ax = fig.add_subplot(111)
line1, = ax.plot(x, y, 'b-')

for phase in np.linspace(0, 10*np.pi, 100):
    line1.set_ydata(np.sin(0.5 * x + phase))
    fig.canvas.draw()
    fig.canvas.flush_events()

Output: