Recommander System

recommender system problem formulation

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—a content based recommendations

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• Notations
  

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• Algorithm(with linear regression)

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• featuring learning

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—Collaborative Filtering
(Low rank matrix fractorization)

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iterating and optimizing both of θ and X

to solve simultaneously for x and theta

(without x0=θ0=1)

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Vectorization

prediction=XΘT

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—Mean Normalization

if there is a person who has never rated for any movie,because of the normalization, we will get a θ with all zero.

In case of this,

then, instead of zero, the value will be replaced of a mean value which means no attitude to it.