机器学习损失函数常用的函数

sigmoid

$\sigma(z) = \frac{1}{1+e^{-z}}$

 1 import matplotlib.pyplot as plt
 2 import numpy as np
 3 import math
 4 import pandas as pd
 5 
 6 z = np.arange(-10.,10.,0.1)
 7 fz =  1/(1 + np.exp(-z))
 8 
 9 plt.plot(z,fz)
10 plt.show()