Multivariate Linear Regression code

In my hand, 30 samples of 4 features and 30 outputs. i want to learn the regression equation of these as;

theta=theta(0) + theta(1) x(1)+ ... + theta(4) x(4)

I am using gradient descent algorithm for this regression analysis. there are three main equations;

for m=1:30;
cost function= J(theta(0)..,theta(4))=1/2m * sum(h(theta)x - y) ^2        
%sum is from 1 to m. x and y are from 1 to m. 

theta(j) := theta(j) - alpha (derivative/derivative theta(j)) J(theta(j)

Thanks

[b]

Sorry for that, i have 30 samples of 3 features output also.

input=30x4 matrix

output=30x3 matrix

Answer 1

[b]

If there is a chance of doing this with 3 features output, it will be superb. otherwise, it's also OK.

Answer 2

[bym]

I really do not understand your question, but perhaps this is what you are looking for:

x = rand(30,4);
>> y = rand(30,1);
>> X = [ones(30,1) x];
>> theta = X\y

theta =

    0.6702
    0.1183
   -0.4163
   -0.1072
   -0.1355

[b]

Actually, no. I have x and y values and theta values will be obtained from the equation.

I want the cost function code.