python drawing --- polynomial fitting

import numpy as np
import matplotlib.pyplot as plt
plt.rcParams['font.sans-serif']=['SimHei'] #用来正常显示中文标签
plt.rcParams['axes.unicode_minus']=False #用来正常显示负号
x=[0.3,0.4,0.7,0.9,1.2,1.9,2.8,3.2,3.7,4.5]
y=[1,2,3,4,5,2,6,9,2,7]
p5=np.polyfit(x,y,5)
y5=np.polyval(p5,x)
p9=np.polyfit(x,y,9)
y9=np.polyval(p9,x)
plt.figure(figsize=(8,8))

plt.plot(x,y,'bo',"原始数据")
plt.plot(x,y5,'r:',"5阶多项式拟合")
plt.plot(x,y9,'g--',"9阶多项式拟合")
plt.legend()
plt.xlabel("x")
plt.ylabel("y")
plt.show()