sigmoid

sigmoid函数：sigmoid.m

function a = sigmoid(X)
for i = 1:size(X,1)
    for j = 1:size(X,2)
        a(i,j) = 1/(1+exp(-X(i,j)));%激活函数
    end
end
end

sigmoid的导数：sigmoid_der.m

%% 此函数为sigmoid的导数

function a = sigmoid_der(x)
a = zeros(size(x));
for i = 1:size(x,1)
    a(i,:) = sigmoid(x(i,:)) *(eye(size(x,2)) - diag(sigmoid(x(i,:))));
end

 

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“手撕”BP算法——使用MATLAB搭建简单的神经网络（附代码）
https://blog.51cto.com/u_15127585/2670111