Vectorization of a gradient descent code

Question

I am implementing a batch gradient descent on Matlab. I have a problem with the update step of theta. theta is a vector of two components (two rows

Answer 1

In addition to the answer given by Mad Physicist, the following can also be applied.

theta = theta - (alpha/m) * sum( (X * theta - y).* X )';

Answer 2

Looks like you are trying to do a simple matrix multiplication, the thing MATLAB is supposedly best at.

theta = theta - (alpha/m) * (X' * (X*theta-y));