Regarding ex-5(week 6) - validationCurve

[SehgalDivij]

In week 6 - exercise 5 - validationCurve.m could you explain why your code works and this doesn't:

for i=1:length(lambda_vec)
	lambda = lambda_vec(i);
	theta = trainLinearReg(X, y, lambda);
	error_train(i) = linearRegCostFunction(X, y, theta, lambda);
	error_val(i) = linearRegCostFunction(Xval, yval, theta, lambda);
end

The above snippet makes perfect sense to me, but it isn't correct.