org.grouplens.lenskit.data.event

Class Ratings

java.lang.Object

org.grouplens.lenskit.data.event.Ratings

public final class Ratings
extends Object

Utilities for working with ratings.

Field Summary

Fields

Modifier and Type	Field and Description
static Ordering<Rating>	ITEM_TIME_COMPARATOR

Constructor Summary

Constructors

Constructor and Description
Ratings()

Method Summary

Modifier and Type	Method and Description
static RatingBuilder	copyBuilder(Rating r) Construct a rating builder initialized with the values of a rating.
static boolean	equals(Rating r1, Rating r2) Compare two ratings for equality.
static int	hashRating(Rating rating) Compute the hash code of a rating.
static MutableSparseVector	itemRatingVector(Collection<? extends Rating> ratings) Construct a rating vector that contains the ratings provided by each user.
static Rating	make(long uid, long iid, double value) Make a fresh rating object with no timestamp.
static Rating	make(long uid, long iid, double value, long ts) Make a fresh rating event.
static RatingBuilder	newBuilder() Construct a new RatingBuilder.
static MutableSparseVector	userRatingVector(Collection<? extends Rating> ratings) Construct a rating vector that contains the ratings provided for each item.
static MutableSparseVector	userRatingVector(Cursor<? extends Rating> ratings) Extract a user rating vector from a rating cursor.

Methods inherited from class java.lang.Object

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

Field Detail

ITEM_TIME_COMPARATOR

public static final Ordering<Rating> ITEM_TIME_COMPARATOR

Constructor Detail

Ratings

public Ratings()

Method Detail

itemRatingVector

public static MutableSparseVector itemRatingVector(@Nonnull
                                                   Collection<? extends Rating> ratings)

Construct a rating vector that contains the ratings provided by each user. If all ratings in ratings are for the same item, then this will be a valid item rating vector. If multiple ratings are by the same user, the one with the highest timestamp is retained. If two ratings by the same user have identical timestamps, then the one that occurs last when the collection is iterated is retained.

Parameters:

ratings - Some ratings (they should all be for the same item)

Returns:

A sparse vector mapping user IDs to ratings.

userRatingVector

public static MutableSparseVector userRatingVector(@Nonnull
                                                   Collection<? extends Rating> ratings)

Construct a rating vector that contains the ratings provided for each item. If all ratings in ratings are by the same user, then this will be a valid user rating vector. If multiple ratings are provided for the same item, the one with the greatest timestamp is retained. Ties are broken by preferring ratings which come later when iterating through the collection.

Parameters:

ratings - A collection of ratings (should all be by the same user)

Returns:

A sparse vector mapping item IDs to ratings

userRatingVector

public static MutableSparseVector userRatingVector(@WillClose
                                                   Cursor<? extends Rating> ratings)

Extract a user rating vector from a rating cursor.

Parameters:

ratings - The rating cursor.

Returns:

The user rating vector.

See Also:

userRatingVector(Collection)

make

public static Rating make(long uid,
                          long iid,
                          double value)

Make a fresh rating object with no timestamp.

See Also:

make(long, long, double, long)

make

public static Rating make(long uid,
                          long iid,
                          double value,
                          long ts)

Make a fresh rating event. Event IDs are generated sequentially. This is mostly useful in test cases.

newBuilder

public static RatingBuilder newBuilder()

Construct a new RatingBuilder.

Returns:

A new rating builder.

Since:

1.3

copyBuilder

public static RatingBuilder copyBuilder(@Nonnull
                                        Rating r)

Construct a rating builder initialized with the values of a rating.

Parameters:

r - The rating.

Returns:

A rating builder that will initially build a copy of r.

Since:

1.e

hashRating

public static int hashRating(Rating rating)

Compute the hash code of a rating. Used to implement Object.hashCode() in rating implementations.

Parameters:

rating - The rating.

Returns:

The rating's hash code.

equals

public static boolean equals(Rating r1,
                             Rating r2)

Compare two ratings for equality. Used to implement Object.equals(Object) in rating implementations.

Parameters:

r1 - The first rating.

r2 - The second rating.

Returns:

Whether the two ratings are equal.