cost代价函数的octave实现

function J = computeCost(X, y, theta)
%COMPUTECOST Compute cost for linear regression
%   J = COMPUTECOST(X, y, theta) computes the cost of using theta as the
%   parameter for linear regression to fit the data points in X and y

% Initialize some useful values
m = length(y); % number of training examples

% You need to return the following variables correctly 
J = 0;

% ====================== YOUR CODE HERE ======================
% Instructions: Compute the cost of a particular choice of theta
%               You should set J to the cost.

h=X*theta-y;
h2 = h.^2;
J = sum(h2)/(2*m);





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

end

代价函数的公式：

因为我对函数和矩阵运算不是很熟悉，只能分布实现代价函数。实现后，感觉还不是很难。