# 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(-2,2,50)) # 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(' y axis')

ax.plot(xdata, ydata, label='sample data')
ax.plot(xdata, 3*xdata**2, label='quadratic')

ax.legend(loc='upper left')
ax.spines['left'].set_position('center')
ax.spines['bottom'].set_position('center')
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')
plt.show()