multilinear regression

X = [1 1 4; 1 2 5; 1 3 8; 1 4 2];
Y = [1; 6; 8; 12];
X_t = transpose(X);
a_h = (inv(X_t * X) * X_t) * Y;
Y_h = X * a_h;
MSE = sqrt(mean((Y_h-Y).^2));
display(MSE);