在week2的computeCost和gradientDescent这两个任务中,总是显示y没有被定义,如何解决这个问题?
computeCost部分的代码:
%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.
J = sum((X*theta-y).^2)/(2*m);
% =========================================================================
end
gradientDescent部分的代码:
%GRADIENTDESCENT Performs gradient descent to learn theta
% theta = GRADIENTDESCENT(X, y, theta, alpha, num_iters) updates theta by
% taking num_iters gradient steps with learning rate alpha
% Initialize some useful values
m = length(y); % number of training examples
J_history = zeros(num_iters, 1);
for iter = 1:num_iters
% ====================== YOUR CODE HERE ======================
% Instructions: Perform a single gradient step on the parameter vector
% theta.
%
% Hint: While debugging, it can be useful to print out the values
% of the cost function (computeCost) and gradient here.
%
theta(1) = theta(1) - alpha*sum(X*theta_s-y)/m;
theta(2) = theta(2) - alpha*sum((X*theta_s-y).*X(:,2))/m;
theta_s = theta;
% ============================================================
Octave输出的结果:
error: 'y' undefined near line 7, column 7
error: called from
computeCost at line 7 column 3
error: 'y' undefined near line 7, column 7
error: called from
gradientDescent at line 7 column 3