1、逻辑回归
逻辑回归与线性回归的主要区别在于假设函数,逻辑回归中的假设函数:
hθ(x) = g(θ'x)=sgmoid(θ’x)
1)sigmoid 代码实现
% sigmoid 代码实现
function g = sigmoid(z)
%SIGMOID Compute sigmoid function
% g = SIGMOID(z) computes the sigmoid of z.
% You need to return the following variables correctly
g = zeros(size(z));
% ====================== YOUR CODE HERE ======================
% Instructions: Compute the sigmoid of each value of z (z can be a matrix,
% vector or scalar).
g = 1 ./ (1 + exp(-z)); % 注意“./”
% =============================================================
end