Compute the cost function for logistic regression

ex2/costFunction.m

@@ -7,7 +7,7 @@ function [J, grad] = costFunction(theta, X, y)
 % Initialize some useful values
 m = length(y); % number of training examples
 
-% You need to return the following variables correctly 
+% You need to return the following variables correctly
 J = 0;
 grad = zeros(size(theta));
 
@@ -19,7 +19,7 @@ grad = zeros(size(theta));
 %
 % Note: grad should have the same dimensions as theta
 %
-
+J = 1/m * (-y'*log(sigmoid(X*theta)) - (1-y)'*log(1-sigmoid(X*theta)));