# 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,ax = plt.subplots()

ax.set_title('premier exemple')
ax.set_xlabel(' x axis')
ax.set_ylabel(' sample')

ax2 = ax.twinx()
ax2.set_ylabel('quadratic')


ax.plot(xdata, ydata, label='sample data')
ax2.plot(xdata, 3*xdata**2, label='quadratic', color='red')
fig.legend()
#ax.legend()
#ax2.legend()
plt.show()