说明：绘制激活函数sigmoid,tanh,relu,elu，直观上了解一下。

#  __author__ = 'czx'
# coding=utf-8
import numpy as np
from numpy import *
import matplotlib
import matplotlib.pyplot as pltdef sigmoid(x):return 1.0/(1.0+exp(-x))def tanh(x):return 2.0/(1.0+exp(-2*x))-1def relu(x):y = x.copy()y[y<0]=0return ydef elu(x,a):y = x.copy()for i in range(y.shape[0]):if y[i]<0:y[i] = a * (exp(y[i])-1)return yif __name__=='__main__':x= arange(-3.0,3.0,0.01)y_sigmoid = sigmoid(x)y_tanh = tanh(x)y_relu = relu(x)y_elu = elu(x,0.25)plt.plot(x,y_sigmoid,'r',linewidth=2.5,label=u'sigmoid')plt.plot(x,y_tanh,'g',linewidth=2.5,label=u'tanh')plt.plot(x,y_relu,'b',linewidth=2.5,label=u'relu')plt.plot(x,y_elu,'k',linewidth=2.5,label=u'elu')plt.ylim([-1,1])plt.xlim([-1,1])plt.legend()plt.grid(color='b' , linewidth='0.3' ,linestyle='--')plt.show()

设置了不同的坐标轴现实范围。