import matplotlib.pyplot as plt
import numpy as np

x=np.arange(2,20,1)
y1=x*x
y2=np.log(x)
fig=plt.figure()
ax1=fig.add_subplot(111)
ax1.plot(x,y1)
ax1.set_ylabel("Y1")
'''
twinx添加一根X坐标轴
'''
ax2=ax1.twinx()
ax2.plot(x,y2,'r')
ax2.set_ylabel("Y2")
ax1.set_xlabel("compare Y1 and Y2")
plt.show()