org.lenskit.basic

Class TopNItemBasedItemRecommender

java.lang.Object

org.lenskit.basic.AbstractItemBasedItemRecommender

org.lenskit.basic.TopNItemBasedItemRecommender

All Implemented Interfaces:

ItemBasedItemRecommender

public class TopNItemBasedItemRecommender
extends AbstractItemBasedItemRecommender

A global item recommender that recommends the top N items from a scorer.

Since:

1.1

Field Summary

Fields

Modifier and Type	Field and Description
protected ItemDAO	itemDAO
protected ItemBasedItemScorer	scorer

Constructor Summary

Constructors

Constructor and Description
TopNItemBasedItemRecommender(ItemDAO idao, ItemBasedItemScorer scorer)

Method Summary

Modifier and Type	Method and Description
protected LongSet	getDefaultExcludes(LongSet items) Get the default exclude set for a item in the global recommendation.
protected ResultList	recommend(int n, ResultMap scores) Pick the top n items from a score vector.
ResultList	recommendRelatedItemsWithDetails(Set<Long> basket, int n, Set<Long> candidates, Set<Long> exclude) Produce a set of recommendations for the item, with details.

Methods inherited from class org.lenskit.basic.AbstractItemBasedItemRecommender

recommendRelatedItems, recommendRelatedItems, recommendRelatedItems, recommendRelatedItems, recommendRelatedItems

Methods inherited from class java.lang.Object

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

Field Detail

itemDAO

protected final ItemDAO itemDAO

scorer

protected final ItemBasedItemScorer scorer

Constructor Detail

TopNItemBasedItemRecommender

@Inject
public TopNItemBasedItemRecommender(ItemDAO idao,
                                             ItemBasedItemScorer scorer)

Method Detail

recommendRelatedItemsWithDetails

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

Description copied from interface: ItemBasedItemRecommender

Produce a set of recommendations for the item, with details. This is the most general recommendation method, allowing the recommendations to be constrained by both a candidate set and an exclude set and potentially providing more details on each recommendation. The exclude set is applied to the candidate set, so the final effective candidate set is candidates minus exclude.

Parameters:

basket - The reference items.

n - The number of ratings to return. If negative, no specific size is requested.

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.

getDefaultExcludes

protected LongSet getDefaultExcludes(LongSet items)

Get the default exclude set for a item in the global recommendation. The base implementation returns the input set.

Parameters:

items - The items for which we are recommending.

Returns:

The set of items to exclude.

recommend

protected ResultList recommend(int n,
                               ResultMap scores)

Pick the top n items from a score vector.

Parameters:

n - The number of items to recommend.

scores - The scored item vector.

Returns:

The top n items from scores, in descending order of score.