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

java.lang.Object
  extended by org.apache.mahout.cf.taste.impl.recommender.AbstractRecommender
      extended by 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
RandomRecommender(DataModel dataModel)
           
 
Method Summary
 float estimatePreference(long userID, long itemID)
           
 List<RecommendedItem> recommend(long userID, int howMany, IDRescorer rescorer)
           
 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, 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)
                                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
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 Refreshable.refresh(Collection) method on some object. This ensure that objects in a refresh dependency graph aren't refreshed twice needlessly.


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