I'm studing the fundamentals of Machine Learning and, when I was reading about the use of Normal Equation in Matlab, I had a question.
If the Normal Equation is:
And
Is the Pseudo Inverse, so:
And pinv(X) compute the pseudo inverse of X.
Why, in Matlab/Octave, some people use:
theta = pinv(X'*X)*X'*y ...(4)
instead of
theta = pinv(X)*y ...(5)
?
Is (4) not redundant? doesn't pinv(X) compute the pseudo inverse formula for us?
Thank you!