如何在 Python 中使用 matplotlib 创建子图

Question

I write this code and I have error in my subplot. I don't now what is wrong in my code. Can you help me ?

import pywt
import scipy.io.wavfile as wavfile

import matplotlib.pyplot as plt

rate,signal = wavfile.read('a0025.wav')
time = [x /rate for x in range(0,len(signal))]
tree = pywt.wavedec(data=signal[:1000], wavelet='db2', level=4, mode='symmetric')
print(len(tree))
newTree = [tree[0]*0, tree[1]*0, tree[2]*0, tree[3]*0, tree[4]]
recSignal = pywt.waverec(newTree,'db2')
fig, ax = plt.subplot(2, 1)
ax[0].plot(time[:1000], signal[:1000])
ax[0].set_xlabel('Czas [s]')
ax[0].set_ylabel('Amplituda')
ax[1].plot(time[:1000], recSignal[:1000])
ax[1].set_xlabel('Czas [s]')
ax[1].set_ylabel('Amplituda')
plt.show()

The error:

 raise ValueError('Illegal argument(s) to subplot: %s' % (args,))
    ValueError: Illegal argument(s) to subplot: (2, 1)

Answer 1

As the error clearly states, you passed an illegal argument to pyplot.subplot() . If you look at the documentation for that function , you'll see that it takes 3 arguments (which can be condensed in one): ax = plt.subplot(2, 1, 1) or ax = plt.subplot(211) .

However, the function that you are looking for is plt.subplots() (note the s at the end), which generates both a figure and an array of subplots :

f, (ax1, ax2) = plt.subplots(1, 2, sharey=True)
ax1.plot(x, y)
ax1.set_title('Sharing Y axis')
ax2.scatter(x, y)

Answer 2

It seems that this bug is in the documentation see https://matplotlib.org/3.2.1/api/_as_gen/matplotlib.pyplot.subplots.html . They forgot the "s" in the third example. The first two examples are correct however.
eg

# using tuple unpacking for multiple Axes
fig, (ax1, ax2) = plt.subplot(1, 2)
fig, ((ax1, ax2), (ax3, ax4)) = plt.subplot(2, 2)