plt_usage_1

import matplotlib.pyplot as plt
import numpy as np

def sigmoid(x):
    return 1. / (1. + np.exp(-x))
 
x = np.arange(-10, 10, 0.1)
y = sigmoid(x)

plt.plot(x, y)
plt.axvline(0.0,ls = 'dotted', color='k')
plt.title(r'Sigmoid函数曲线', fontsize = 15)
plt.text(5,0.8,r'$y = \frac{1}{1+e^{-z}}$', fontsize = 18)

plt.show()