import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import math

print(2**2)
print(2**3)
print(2**(-2))
print(2**(-3))

[OUT]:

4
8
0.25
0.125

math.e

[OUT]:

2.718281828459045

Sigmoid (시그모이드  함수)

x<0 : 0.5미만, x>=0: 0.5이상의 값을 뱉음

def sigmoid(z):
    return 1/(1+math.e**(-z))

print(sigmoid(-100))
print(sigmoid(-10))
print(sigmoid(-1))
print(sigmoid(0))
print(sigmoid(1))
print(sigmoid(10))
print(sigmoid(100))

[OUT]:

3.7200759760208555e-44
4.539786870243442e-05
0.2689414213699951
0.5
0.7310585786300049
0.9999546021312976
1.0

시각화

for z in np.linspace(-10,10,50):
    s = sigmoid(z)
    plt.plot(z,s,'ro')
plt.show()

review
- sigmoid 함수는 y를 0~1 범위로 변환