python实现并绘制 sigmoid函数，tanh函数，ReLU函数，PReLU函数

2018/12/28 12:20

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# -*- coding:utf-8 -*-
from matplotlib import pyplot as plt
import numpy as np
import mpl_toolkits.axisartist as axisartist

def sigmoid(x):
return 1. / (1 + np.exp(-x))

def tanh(x):
return (np.exp(x) - np.exp(-x)) / (np.exp(x) + np.exp(-x))

def relu(x):
return np.where(x&lt;0,0,x)

def prelu(x):
return np.where(x&lt;0,0.5*x,x)

def plot_sigmoid():
x = np.arange(-10, 10, 0.1)
y = sigmoid(x)
fig = plt.figure()
ax = axisartist.Subplot(fig,111)
ax.spines['top'].set_color('none')
ax.spines['right'].set_color('none')
# ax.spines['bottom'].set_color('none')
# ax.spines['left'].set_color('none')
ax.axis['bottom'].set_axisline_style("-|&gt;",size=1.5)
ax.spines['left'].set_position(('data', 0))
ax.plot(x, y)
plt.xlim([-10.05, 10.05])
plt.ylim([-0.02, 1.02])
plt.tight_layout()
plt.savefig("sigmoid.png")
plt.show()

def plot_tanh():
x = np.arange(-10, 10, 0.1)
y = tanh(x)
fig = plt.figure()
ax.spines['top'].set_color('none')
ax.spines['right'].set_color('none')
# ax.spines['bottom'].set_color('none')
# ax.spines['left'].set_color('none')
ax.spines['left'].set_position(('data', 0))
ax.spines['bottom'].set_position(('data', 0))
ax.plot(x, y)
plt.xlim([-10.05, 10.05])
plt.ylim([-1.02, 1.02])
ax.set_yticks([-1.0, -0.5, 0.5, 1.0])
ax.set_xticks([-10, -5, 5, 10])
plt.tight_layout()
plt.savefig("tanh.png")
plt.show()

def plot_relu():
x = np.arange(-10, 10, 0.1)
y = relu(x)
fig = plt.figure()
ax.spines['top'].set_color('none')
ax.spines['right'].set_color('none')
# ax.spines['bottom'].set_color('none')
# ax.spines['left'].set_color('none')
ax.spines['left'].set_position(('data', 0))
ax.plot(x, y)
plt.xlim([-10.05, 10.05])
plt.ylim([0, 10.02])
ax.set_yticks([2, 4, 6, 8, 10])
plt.tight_layout()
plt.savefig("relu.png")
plt.show()

def plot_prelu():
x = np.arange(-10, 10, 0.1)
y = prelu(x)
fig = plt.figure()
ax.spines['top'].set_color('none')
ax.spines['right'].set_color('none')
# ax.spines['bottom'].set_color('none')
# ax.spines['left'].set_color('none')
ax.spines['left'].set_position(('data', 0))
ax.spines['bottom'].set_position(('data', 0))
ax.plot(x, y)
plt.xticks([])
plt.yticks([])
plt.tight_layout()
plt.savefig("prelu.png")
plt.show()

if __name__ == "__main__":
plot_sigmoid()
plot_tanh()
plot_relu()
plot_prelu()



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