# coding = utf8
import matplotlib.pyplot as plt
import numpy as np
import scipy as sci

xdata = np.linspace(-1,1,50) # [-1;1] échantilloné sur 50 valeurs
ydata = np.array(np.random.uniform(17,20,50)) # 50 valeurs au hasard entre -2 et 2

fig,(ax1,ax2) = plt.subplots(2,1)

ax1.plot(xdata, ydata)
ax2.plot(xdata, 2*ydata)

plt.show()