How to update a plot in Matplotlib?

How to update a plot in Matplotlib?

Last Updated : 17 Mar, 2021

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:

update plot matplotlib

How to update a plot in Matplotlib?

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