org.grouplens.lenskit.baseline

Class UserMeanItemScorer

java.lang.Object

org.grouplens.lenskit.basic.AbstractItemScorer

org.grouplens.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(UserEventDAO dao, ItemScorer base, UserHistorySummarizer sum, double damp) Construct a scorer that computes user means offset by the global mean.

Method Summary

Modifier and Type	Method and Description
void	score(long user, MutableSparseVector items) Score items in a vector.
String	toString()

Methods inherited from class org.grouplens.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(UserEventDAO dao,
                                  @UserMeanBaseline
                                  ItemScorer base,
                                  UserHistorySummarizer sum,
                                  @MeanDamping
                                  double damp)

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

Parameters:

dao - The DAO to get user ratings.

base - An item scorer that provides the baseline scores.

sum - The summarizer for getting user histories.

damp - A damping term for the calculations.

Method Detail

score

public void score(long user,
                  @Nonnull
                  MutableSparseVector items)

Description copied from interface: ItemScorer

Score items in a vector. The key domain of the provided vector is the items to score, and the score method sets the values for each item to its score (or unsets it, if no score can be provided). The previous values are discarded.

Parameters:

user - The user ID.

items - The score vector.

toString

public String toString()

Overrides:

toString in class Object