Normal equation in linear regression
From coursera's ML course I've known that the normal equation is calculated as follows:
pinv((X'*X))*X'*Y; (octave code) but apparently this is equivalent to just pinv(X)*Y; Can anyone explain why this is the case? 
Re: Normal equation in linear regression
Quote:

Re: Normal equation in linear regression
Dr. Ng derived the Normal Equation in class, see Lecture 46 and he also cautioned about the case where X'*X is noninvertible which meant that there were redundant features (linearly dependent) or too many features (m <= n).
Daniel 
Re: Normal equation in linear regression
Thanks you all for useful input. We have some reading to do... :)

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