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jiunjiunma (3) [Avatar] Offline
I am reading the code for recommendation using SVD (listing 14.3). I understand you are trying to transform the original matrix to a lower-dimension space but why is it calculated as dataMat.T * U [:, :4] * Sig4.I? (Care to help us refreshing our linear algebra?)
Also, the text is referring to a 3-dimensional space (Sig3), but the code is referring a 4-dimension space (Sig4). There seems to be some typos there.

395823 (1) [Avatar] Offline
I have the same doubt about the transformed items. Maybe it is a trivial question for someone with high skills in linear algebra, i dont know... but I found that:

representation of itens in latent space = representation of items * V * Sigma.I

I really dont know how to justify xformedItems = dataMat.T * U[:,:4] * Sig4.I

This code is obscure to me. Could someone help me?