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）;


%?=========================================================================

end