org.grouplens.lenskit.baseline

Class ConstantItemScorer

java.lang.Object

org.grouplens.lenskit.baseline.ConstantItemScorer

All Implemented Interfaces:

Serializable, ItemScorer

Direct Known Subclasses:

GlobalMeanRatingItemScorer

@Shareable
public class ConstantItemScorer
extends Object
implements ItemScorer, Serializable

Rating scorer that predicts a constant rating for all items.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	ConstantItemScorer.Value Parameter: the value used by the constant scorer.

Constructor Summary

Constructors

Constructor and Description
ConstantItemScorer(double val) Construct a new constant scorer.

Method Summary

Modifier and Type	Method and Description
SparseVector	score(long user, Collection<Long> items) Score a collection of items.
double	score(long user, long item) Score a single item.
void	score(long user, MutableSparseVector output) Score items in a vector.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ConstantItemScorer

@Inject
public ConstantItemScorer(@ConstantItemScorer.Value
                                  double val)

Construct a new constant scorer. This is exposed so other code can use it as a fallback.

Parameters:

val - The value to use.

Method Detail

score

public double score(long user,
                    long item)

Description copied from interface: ItemScorer

Score a single item.

Specified by:

score in interface ItemScorer

Parameters:

user - The user ID for whom to generate a score.

item - The item ID to score.

Returns:

The score, or Double.NaN if no score can be generated.

score

@Nonnull
public SparseVector score(long user,
                                   @Nonnull
                                   Collection<Long> items)

Description copied from interface: ItemScorer

Score a collection of items.

Specified by:

score in interface ItemScorer

Parameters:

user - The user ID for whom to generate scores.

items - The item to score.

Returns:

A mapping from item IDs to predicted preference. This mapping may not contain all requested items.

score

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

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.

Specified by:

score in interface ItemScorer

Parameters:

user - The user ID.

output - The score vector.

toString

public String toString()

Overrides:

toString in class Object