Rating predictor using OrdRec to map scores to ratings.
The model views user feedback as ordinal. The framework is based on
a pointwise (rather than pairwise) ordinal approach, it can wrap existing
CF methods, and upgrade them into being able to tackle ordinal feedback.
The implementation is based on Koren's paper:
Predict for items in a vector. The key domain of the provided vector is the items whose
predictions are requested, and the predict method sets the values for each item to its
predict (or unsets it, if no prediction can be provided). The previous values are discarded.
uid - The user ID.
predictions - The prediction output vector. Its key domain is the items to score.