파이썬 함수

import numpy as np 

cross_entropy_error()

y =np.array([[0.1, 0.05, 0.6, 0.0, 0.05, 0.1, 0, 0.1, 0, 0], [0.1, 0.05, 0.1, 0, 0.05, 0.1, 0, 0.6, 0, 0]])
t = np.array([[0, 0, 1, 0, 0, 0, 0, 0, 0, 0], [0, 0, 1, 0, 0, 0, 0, 0, 0, 0]])

def cross_entropy_error(y, t):
 if y.ndim == 1:
 t = t.reshape(1, t.size)
 y = y.reshape(1, y.size) 
 batch_size = y.shape[0]
 #return -np.sum(t * np.log(y + 1e-7))
 return -np.sum(t * np.log(y + 1e-7)) / batch_size

>>> cross_entropy_error(y, t)
1.406704775046942

softmax()

x = np.array([[0.3,2.9,4.0], [0.3,2.9,4.0]])

def softmax(x):
 if x.ndim == 2:
 x = x.T
 x = x - np.max(x, axis=0)
 y = np.exp(x) / np.sum(np.exp(x), axis=0)
 return y.T 
 x = x - np.max(x) # 오버플로 대책
 return np.exp(x) / np.sum(np.exp(x))

>>> softmax(x)
array([[0.01821127, 0.24519181, 0.73659691],
 [0.01821127, 0.24519181, 0.73659691]])