org.apache.mahout.cf.taste.impl.recommender

Class RandomRecommender

java.lang.Object

org.apache.mahout.cf.taste.impl.recommender.AbstractRecommender

org.apache.mahout.cf.taste.impl.recommender.RandomRecommender

All Implemented Interfaces:

Refreshable, Recommender

public final class RandomRecommender
extends AbstractRecommender

Produces random recommendations and preference estimates. This is likely only useful as a novelty and for benchmarking.

Constructor Summary

Constructors

Constructor and Description
RandomRecommender(DataModel dataModel)

Method Summary

Modifier and Type	Method and Description
float	estimatePreference(long userID, long itemID)
List<RecommendedItem>	recommend(long userID, int howMany, IDRescorer rescorer, boolean includeKnownItems)
void	refresh(Collection<Refreshable> alreadyRefreshed) Triggers "refresh" -- whatever that means -- of the implementation.

Methods inherited from class org.apache.mahout.cf.taste.impl.recommender.AbstractRecommender

getAllOtherItems, getDataModel, getDefaultCandidateItemsStrategy, recommend, recommend, recommend, removePreference, setPreference

Methods inherited from class java.lang.Object

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

Constructor Detail

RandomRecommender

public RandomRecommender(DataModel dataModel)
                  throws TasteException

Throws:

TasteException

Method Detail

recommend

public List<RecommendedItem> recommend(long userID,
                                       int howMany,
                                       IDRescorer rescorer,
                                       boolean includeKnownItems)
                                throws TasteException

Parameters:

userID - user for which recommendations are to be computed

howMany - desired number of recommendations

rescorer - rescoring function to apply before final list of recommendations is determined

includeKnownItems - whether to include items already known by the user in recommendations

Returns:

List of recommended RecommendedItems, ordered from most strongly recommend to least

Throws:

TasteException - if an error occurs while accessing the DataModel

estimatePreference

public float estimatePreference(long userID,
                                long itemID)

Parameters:

userID - user ID whose preference is to be estimated

itemID - item ID to estimate preference for

Returns:

an estimated preference if the user has not expressed a preference for the item, or else the user's actual preference for the item. If a preference cannot be estimated, returns Double.NaN

refresh

public void refresh(Collection<Refreshable> alreadyRefreshed)

Description copied from interface: Refreshable

Triggers "refresh" -- whatever that means -- of the implementation. The general contract is that any Refreshable should always leave itself in a consistent, operational state, and that the refresh atomically updates internal state from old to new.

Parameters:

alreadyRefreshed - Refreshables that are known to have already been refreshed as a result of an initial call to a {#refresh(Collection)} method on some object. This ensure that objects in a refresh dependency graph aren't refreshed twice needlessly.