python使用Matplotlib绘制分段函数

# coding:utf-8
 
"""
Author: roguesir
Date: 2017/8/30
GitHub: https://roguesir.github.com
Blog: http://blog.csdn.net/roguesir
"""
 
import numpy as np
import matplotlib.pyplot as plt
 
def sgn(value):
 if value < 4:
 return 20
 else:
 return 15
plt.figure(figsize=(6,4))
x = np.linspace(0, 8, 100)
y = np.array([])
for v in x:
 y = np.append(y,np.linspace(sgn(v),sgn(v),1))
l=plt.plot(x,y,'b',label='type')
plt.legend()
plt.show()