用matlab实现线性回归,线性回归代码实现（matlab）

1 代价函数实现(cost function)

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.

predictions = X * theta;

sqrErrors = (predictions-y) .^ 2;

J = 1/(2*m) * sum(sqrErrors);

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