######后期会更新

import matplotlib.pyplot as plt
from matplotlib.pyplot import MultipleLocator
import numpy as np
import math

plt.rcParams['font.sans-serif'] = ['SimHei']
plt.rcParams['axes.unicode_minus'] = False

# sigmoid激活函数用的最少，但为二分类问题时，可作为输出层会出现梯度消失（即当x趋于无穷大或无穷小时会使得导数趋于0）

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

# ReLU  
def ReLU(x):
    return np.maximum(0, 0.1 * x)  

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

x1 = np.arange(-10.0, 10.0, 0.1)
y1 = sigmoid(x1)
y2 = ReLU(x1)
y3 = tanh(x1)
plt.rc('font', family='Times New Roman', size=13)  # 全局中英文为字体“罗马字体”
# plt.rcParams['xtick.direction'] = 'in'
# plt.rcParams['ytick.direction'] = 'in'
plt.plot(x1, y1, label='sigmoid')
plt.plot(x1, y2, label='ReLU')
plt.plot(x1, y3, label='tanh')
plt.xlabel('X1')
plt.ylabel('Scores of Diff-act')
plt.grid(True)
plt.legend(loc="lower right")

"""去掉图上边框，与右边框"""
ax = plt.gca()
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')
plt.show()