[신경망]교차 엔트로피 오차

[주인장]

# 교차 엔트로피 오차
import numpy as np

def cross_entropy_error(y, t):
    delta = 1e-7
    return -np.sum(t * np.log(y + delta))

def cross_entropy_error2(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)) / batch_size   # 평균 교차 엔트로피 


y = [0.1, 0.05, 0.6, 0.0, 0.05, 0.1, 0.0, 0.1, 0.0, 0.0]
t = [0,0,1,0,0,0,0,0,0,0]
print(cross_entropy_error(np.array(y), np.array(t)))    # 0에 가까울 수록 정답

y = [0.1, 0.05, 0.1, 0.0, 0.05, 0.1, 0.0, 0.6, 0.0, 0.0]
print(cross_entropy_error(np.array(y), np.array(t)))