OpenRouter vs recommenderlab

recommenderlab provides the rating matrix classes, recommender algorithms and evaluation schemes used to benchmark collaborative filtering in R. The algorithm surface has been settled since 0.2-6 added hybrid recommenders and 0.2-5 added a LIBMF-based one. Every release since has been reactive: sparse matrix coercion changes from Matrix, a cosine similarity fix from proxy, and most recently a dissimilarity change inherited from arules.

The package sits on a stack it does not control — Matrix, proxy and arules — and the release notes read as a log of that stack moving. Three separate releases exist to track Matrix coercion and row/colSums changes alone. The genuine user-facing work now goes into evaluation ergonomics rather than algorithms: dropping users with too few ratings with a warning, making UBCF work when fewer than n neighbors exist, and accepting tibbles in coercion.

The next release will most likely respond to another change in Matrix, proxy or arules, which have driven the last four. The 0 versus NA handling in sparse matrices flagged in 1.0-7 is the open thread most likely to need follow-up.