Hello, I've read Mahout in Action book; then this paper - "Case Study Evaluation of Mahout as a Recommender Platform" ( http://ir.ii.uam.es/rue2012/papers/rue2012-seminario.pdf); and then this Sean Owen's comment ( http://mail-archives.apache.org/mod_mbox/mahout-user/201210.mbox/%3CCAEccTyzRzhRzUi9FGCPhPqa01bei=wyctx2kewocpfvu37p...@mail.gmail.com%3E) and now I am confused what formula is used for user-based (and item-based) recommendations. What paper is it based on?
Does it use mean centering as in the formula in Resnick's paper ( http://dl.acm.org/citation.cfm?id=192905) or formula 4.15 in "A Comprehensive Survey of Neighborhood-based Recommendation Methods" ( http://www.springerlink.com/content/n3jq77686228781n/)? Or authors of "Case Study Evaluation of Mahout as a Recommender Platform" are right and it computed recommendation somehow similar to formula 4.12 in "A Comprehensive Survey of Neighborhood-based Recommendation Methods"? Following the algorithm in the Mahout in Action book, does not seem like i uses mean centering. However, in the section about Cosine similarity, authors states that the input it mean centered. Thank you. -- Best Regards, Evgeny Karataev
