function g = sigmoid(z)
%SIGMOID Compute sigmoid functoon
%   J = 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 .+ e .^ -z);
g = 1.0 ./ (1.0 + exp(-z));%exp(n)-->e的n次方



% =============================================================

end