출력층의 활성화 함수는 풀고자 하는 문제의 성질에 맞게 정합니다. 예를 들어 회귀에는 항등 함수
를,
2
클래스 분류에는 시그모이드 함수를, 다중 클래스 분류에는 소프트맥스 함수를 사용하는 것이 일반적입
니다. 출력층의 활성화 함수에 대해서는 다음에 다시 자세히 설명합니다.
3.4.3
구현 정리
이로써
3
층 신경망에 대한 설명은 끝입니다. 그럼 지금까지의 구현을 정리해보도록 하죠. 신경
망 구현의 관례에 따라 가중치만
W1
과 같이 대문자로 쓰고, 그 외 편향과 중간 결과 등은 모두
소문자로 썼습니다.
def init
_
network
():
network
=
{}
network
['
W1
']
=
np
.
array
([[
0
.
1
,
0
.
3
,
0
.
5
],
[
0
.
2
,
0
.
4
,
0
.
6
]])
network
['
b1
']
=
np
.
array
([
0
.
1
,
0
.
2
,
0
.
3
])
network
['
W2
']
=
np
.
array
([[
0
.
1
,
0
.
4
],
[
0
.
2
,
0
.
5
],
[
0
.
3
,
0
.
6
]])
network
['
b2
']
=
np
.
array
([
0
.
1
,
0
.
2
])
network
['
W3
']
=
np
.
array
([[
0
.
1
,
0
.
3
],
[
0
.
2
,
0
.
4
]])
network
['
b3
']
=
np
.
array
([
0
.
1
,
0
.
2
])
return network
def forward
(
network
,
x
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