CODEWITHSUNDEEP
pythonmatplotlib
Julian Helfferich
Julian Helfferich

Reputation: 1310

pyplot: Add graph to existing plot

In order to draw two graphs in one plot with python's matplotlib.pyplot, one would typically do this:

import matplotlib.pyplot as plt

xdata = [0, 1, 2, 3, 4]
ydata1 = [0, 1, 2, 3, 4]
ydata2 = [0, 0.5, 2, 4.5, 8]

plt.plot(xdata, ydata1, 'r-', xdata, ydata2, 'b--')
plt.show()

However, I would like to draw the second dataset only under certain circumstances, like this:

plt.plot(xdata, ydata1, 'r-')

if DrawSecondDataset:
    plt.plot(data, ydata2, 'b--')

Unfortunately, calling plot for the second time means that the first dataset is erased.

How can you add a graph to an already existing plot?

EDIT:

As the answers pointed out correctly, the dataset is only erased if plt.show() has been called between the two plt.plot() commands. Thus, the example above actually shows both datasets.

For completeness: Is there an option to add a graph to an existing plot on which plt.show() has already been called? Such as

plt.plot(xdata, ydata1, 'r-')
plt.show()

...

plt.plot(data, ydata2, 'b--')
plt.show()

Upvotes: 5

Views: 21792

Answers (3)

Alejo Bernardin
Alejo Bernardin

Reputation: 1215

The first data won't be erased in this way

plt.plot(xdata, ydata1, 'r-')

if DrawSecondDataset:
    plt.plot(data, ydata2, 'b--')

plt.show()

Upvotes: 0

Taufiq Rahman
Taufiq Rahman

Reputation: 5704

if DrawSecondDataset:
    plt.plot(data, ydata2, 'b--')
    plt.show() #to display it

Upvotes: 0

nick_name
nick_name

Reputation: 1373

Just call show() at the very end.

Upvotes: 2

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