title: Matrix factorization for collaborative filtering - new users and items?
body: <p>I've been reading about using matrix factorization for collaborative filtering, but I can't seem to find an example that deals with adding a new user or item to the system, or having the user rate a new item. In these cases, the item-user matrix and the factorization needs to be recomputed, correct? How can this perform well with a large number of users and items? Is there a way around it?</p>
  
  <p>Thank you</p>