org.lenskit.baseline

Class UserMeanItemScorer

java.lang.Object

org.lenskit.basic.AbstractItemScorer

org.lenskit.baseline.UserMeanItemScorer

All Implemented Interfaces:

ItemScorer

public class UserMeanItemScorer
extends AbstractItemScorer

Rating scorer that returns the user’s average rating for all predictions.

This scorer does not directly average the user’s ratings; rather, it averages their offsets from the scores produced by another scorer (the UserMeanBaseline). If this is the GlobalMeanRatingItemScorer (the default), then this is a straight user mean item scorer with damping; reconfigure it to use ItemMeanRatingItemScorer as the baseline to get a user-item personalized mean.

This is why it is not called a mean rating item scorer; it can compute the mean of any kind of user-based score.

Constructor Summary

Constructors

Constructor and Description
UserMeanItemScorer(RatingVectorPDAO rv, ItemScorer base, double damp) Construct a scorer that computes user means offset by the global mean.

Method Summary

Modifier and Type	Method and Description
ResultMap	scoreWithDetails(long user, java.util.Collection<java.lang.Long> items) Score a collection of items and potentially return more details on the scores.
java.lang.String	toString()

Methods inherited from class org.lenskit.basic.AbstractItemScorer

score, score

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

UserMeanItemScorer

@Inject
public UserMeanItemScorer(RatingVectorPDAO rv,
                                  @UserMeanBaseline
                                  ItemScorer base,
                                  @MeanDamping
                                  double damp)

Construct a scorer that computes user means offset by the global mean.

Parameters:

rv - The DAO to get user rating vectors.

base - An item scorer that provides the baseline scores.

damp - A damping term for the calculations.

Method Detail

scoreWithDetails

@Nonnull
public ResultMap scoreWithDetails(long user,
                                           @Nonnull
                                           java.util.Collection<java.lang.Long> items)

Description copied from interface: ItemScorer

Score a collection of items and potentially return more details on the scores.

Parameters:

user - The user ID for whom to generate scores.

items - The item to score.

Returns:

The scores for the items. This result set may not contain all requested items. Implementations that support additional details will return a subclass of ResultMap that provides access to those details.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object