为什么 plt.cla() 只适用于其中一个地块？

Question

I am trying to create a program that has two different plots at the same time:

import matplotlib.pyplot as plt
import numpy as np

plt.ion()


for i in range(100):
    x = np.arange(i, i + 50, 0.2)

    plt.cla()

    for subplotId in range(1, 3):
        plt.subplot(2, 1, subplotId)
        plt.ylim(-100, 100)

        y = np.tan(x)
        plt.plot(x, y)

    plt.pause(0.1)

However, plt.cla() only seems to work on the second plot. The first plot seems to get 'squished': How do I clear both plots?

Answer 1

The problem is that plt.cla() only works on the current subplot. To fix the problem you need to run it after each subplot, like:

import matplotlib.pyplot as plt
import numpy as np

plt.ion()


for i in range(100):
    x = np.arange(i, i + 50, 0.2)
    #don't put plt.cla() here

    for subplotId in range(1, 3):
        plt.subplot(2, 1, subplotId)
        plt.cla() # put it here so that it runs for each subplot
        plt.ylim(-100, 100)

        y = np.tan(x)
        plt.plot(x, y)

    plt.pause(0.1)

I hope this helps.