org.lenskit.basic

Class PopularItemRecommender

java.lang.Object

org.lenskit.basic.AbstractItemRecommender

org.lenskit.basic.PopularItemRecommender

All Implemented Interfaces:

ItemBasedItemRecommender, ItemRecommender

public class PopularItemRecommender
extends AbstractItemRecommender
implements ItemRecommender, ItemBasedItemRecommender

Recommend the most popular items. More efficient than using a popularity rank scorer.

Constructor Summary

Constructors

Constructor and Description
PopularItemRecommender(InteractionStatistics stats, DataAccessObject dao) Create a new popular item recommender.

Method Summary

Modifier and Type	Method and Description
protected LongList	recommend(long user, int n, LongSet candidates, LongSet exclude) Primary method for implementing an item recommender without details.
java.util.List<java.lang.Long>	recommendRelatedItems(long reference) Recommend all possible items for a reference item using the default exclude set.
java.util.List<java.lang.Long>	recommendRelatedItems(long reference, int n) Recommend up to n possible items for a reference item using the default exclude set.
java.util.List<java.lang.Long>	recommendRelatedItems(java.util.Set<java.lang.Long> basket) Recommend all possible items for a set of reference items using the default exclude set.
java.util.List<java.lang.Long>	recommendRelatedItems(java.util.Set<java.lang.Long> basket, int n) Recommend up to n items for a set of reference items using the default exclude set.
LongList	recommendRelatedItems(java.util.Set<java.lang.Long> basket, int n, java.util.Set<java.lang.Long> candidates, java.util.Set<java.lang.Long> exclude) Produce a set of recommendations for the item.
ResultList	recommendRelatedItemsWithDetails(java.util.Set<java.lang.Long> basket, int n, java.util.Set<java.lang.Long> candidates, java.util.Set<java.lang.Long> exclude) Produce a set of recommendations for the item, with details.
protected ResultList	recommendWithDetails(long user, int n, LongSet candidates, LongSet exclude) Primary method for implementing an item recommender.

Methods inherited from class org.lenskit.basic.AbstractItemRecommender

recommend, recommend, recommend, recommendWithDetails

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.lenskit.api.ItemRecommender

recommend, recommend, recommend, recommendWithDetails

Constructor Detail

PopularItemRecommender

@Inject
public PopularItemRecommender(InteractionStatistics stats,
                                      DataAccessObject dao)

Create a new popular item recommender.

Parameters:

stats - The interaction statistics.

Method Detail

recommendRelatedItems

public java.util.List<java.lang.Long> recommendRelatedItems(long reference)

Description copied from interface: ItemBasedItemRecommender

Recommend all possible items for a reference item using the default exclude set.

Specified by:

recommendRelatedItems in interface ItemBasedItemRecommender

Parameters:

reference - The reference item.

Returns:

The recommended items.

See Also:

ItemBasedItemRecommender.recommendRelatedItems(Set, int, Set, Set)

recommendRelatedItems

public java.util.List<java.lang.Long> recommendRelatedItems(long reference,
                                                            int n)

Description copied from interface: ItemBasedItemRecommender

Recommend up to n possible items for a reference item using the default exclude set.

Specified by:

recommendRelatedItems in interface ItemBasedItemRecommender

Parameters:

reference - The reference item.

n - The number of items to recommend. If negative, recommend as many as possible.

Returns:

The recommended items.

See Also:

ItemBasedItemRecommender.recommendRelatedItems(Set, int, Set, Set)

recommendRelatedItems

public java.util.List<java.lang.Long> recommendRelatedItems(java.util.Set<java.lang.Long> basket)

Description copied from interface: ItemBasedItemRecommender

Recommend all possible items for a set of reference items using the default exclude set.

Specified by:

recommendRelatedItems in interface ItemBasedItemRecommender

Parameters:

basket - The reference items.

Returns:

The recommended items.

See Also:

ItemBasedItemRecommender.recommendRelatedItems(Set, int, Set, Set)

recommendRelatedItems

public java.util.List<java.lang.Long> recommendRelatedItems(java.util.Set<java.lang.Long> basket,
                                                            int n)

Description copied from interface: ItemBasedItemRecommender

Recommend up to n items for a set of reference items using the default exclude set.

Specified by:

recommendRelatedItems in interface ItemBasedItemRecommender

Parameters:

basket - The reference items.

n - The number of recommendations to return. If negative, recommend as many as possible.

Returns:

The recommended items.

See Also:

ItemBasedItemRecommender.recommendRelatedItems(Set, int, Set, Set)

recommendRelatedItems

public LongList recommendRelatedItems(java.util.Set<java.lang.Long> basket,
                                      int n,
                                      @Nullable
                                      java.util.Set<java.lang.Long> candidates,
                                      @Nullable
                                      java.util.Set<java.lang.Long> exclude)

Description copied from interface: ItemBasedItemRecommender

Produce a set of recommendations for the item. This is the most general recommendation method, allowing the recommendations to be constrained by both a candidate set \(\mathcal{C}\) and an exclude set \(\mathcal{E}\). The exclude set is applied to the candidate set, so the final effective candidate set is \(\mathcal{C} \backslash \mathcal{E}\).

The recommender is not guaranteed to return a full n recommendations. There are many reasons why it might return a shorter list, including lack of items, lack of coverage for items, or a predefined notion of a maximum recommendation list length. However, a negative value for n instructs the recommender to return as many as it can consistent with any limitations built in to its design and/or supporting algorithms.

Specified by:

recommendRelatedItems in interface ItemBasedItemRecommender

Parameters:

basket - The reference items.

n - The number of ratings to return. If negative, recommend as many as possible.

candidates - A set of candidate items which can be recommended. If null, all items are considered candidates.

exclude - A set of items to be excluded. If null, a default exclude set is used.

Returns:

A list of recommended items.

recommendRelatedItemsWithDetails

public ResultList recommendRelatedItemsWithDetails(java.util.Set<java.lang.Long> basket,
                                                   int n,
                                                   @Nullable
                                                   java.util.Set<java.lang.Long> candidates,
                                                   @Nullable
                                                   java.util.Set<java.lang.Long> exclude)

Description copied from interface: ItemBasedItemRecommender

Produce a set of recommendations for the item, with details. This method functions identically to ItemBasedItemRecommender.recommendRelatedItems(Set, int, Set, Set), except that it returns more detailed results.

Specified by:

recommendRelatedItemsWithDetails in interface ItemBasedItemRecommender

Parameters:

basket - The reference items.

n - The number of ratings to return. If negative, recommend as many as possible.

candidates - A set of candidate items which can be recommended. If null, all items are considered candidates.

exclude - A set of items to be excluded. If null, a default exclude set is used.

Returns:

A list of recommended items with recommendation details. If the recommender cannot assign meaningful scores, the scores will be Double.NaN.

recommend

protected LongList recommend(long user,
                             int n,
                             @Nullable
                             LongSet candidates,
                             @Nullable
                             LongSet exclude)

Description copied from class: AbstractItemRecommender

Primary method for implementing an item recommender without details. The default implementation delegates to AbstractItemRecommender.recommendWithDetails(long, int, LongSet, LongSet).

Overrides:

recommend in class AbstractItemRecommender

Parameters:

user - The user ID.

n - The number of recommendations to produce, or a negative value to produce unlimited recommendations.

candidates - The candidate items, or null for default.

exclude - The exclude set, or null for default.

Returns:

The result list.

See Also:

AbstractItemRecommender.recommend(long, int, Set, Set)

recommendWithDetails

protected ResultList recommendWithDetails(long user,
                                          int n,
                                          @Nullable
                                          LongSet candidates,
                                          @Nullable
                                          LongSet exclude)

Description copied from class: AbstractItemRecommender

Primary method for implementing an item recommender.

Specified by:

recommendWithDetails in class AbstractItemRecommender

Parameters:

user - The user ID.

n - The number of recommendations to produce, or a negative value to produce unlimited recommendations.

candidates - The candidate items, or null for default.

exclude - The exclude set, or null for default.

Returns:

The result list.

See Also:

AbstractItemRecommender.recommendWithDetails(long, int, Set, Set)