com.planetj.taste.impl.recommender
Class ItemUserAverageRecommender

java.lang.Object
  com.planetj.taste.impl.recommender.AbstractRecommender
      com.planetj.taste.impl.recommender.ItemUserAverageRecommender

All Implemented Interfaces:

Refreshable, Recommender

public final class ItemUserAverageRecommender
extends AbstractRecommender

Like ItemAverageRecommender, except that estimated preferences are adjusted for the Users' average preference value. For example, say user X has not rated item Y. Item Y's average preference value is 3.5. User X's average preference value is 4.2, and the average over all preference values is 4.0. User X prefers items 0.2 higher on average, so, the estimated preference for user X, item Y is 3.5 + 0.2 = 3.7.

Since:

1.4

Author:

Sean Owen

Constructor Summary

ItemUserAverageRecommender(DataModel dataModel)

Method Summary

double	estimatePreference(java.lang.Object userID, java.lang.Object itemID)
java.util.List<RecommendedItem>	recommend(java.lang.Object userID, int howMany, Rescorer<Item> rescorer)
void	refresh() 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.
void	removePreference(java.lang.Object userID, java.lang.Object itemID) Default implementation which just calls DataModel.removePreference(Object, Object) (Object, Object)}.
void	setPreference(java.lang.Object userID, java.lang.Object itemID, double value) Default implementation which just calls DataModel.setPreference(Object, Object, double).
java.lang.String	toString()

Methods inherited from class com.planetj.taste.impl.recommender.AbstractRecommender

getAllOtherItems, getDataModel, recommend

Methods inherited from class java.lang.Object

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

Constructor Detail

ItemUserAverageRecommender

public ItemUserAverageRecommender(DataModel dataModel)

Method Detail

recommend

@NotNull
public java.util.List<RecommendedItem> recommend(java.lang.Object userID,
                                                         int howMany,
                                                         Rescorer<Item> 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 double estimatePreference(java.lang.Object userID,
                                 java.lang.Object itemID)
                          throws TasteException

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

Throws:

TasteException - if an error occurs while accessing the DataModel

setPreference

public void setPreference(java.lang.Object userID,
                          java.lang.Object itemID,
                          double value)
                   throws TasteException

Default implementation which just calls DataModel.setPreference(Object, Object, double).

Specified by:

setPreference in interface Recommender

Overrides:

setPreference in class AbstractRecommender

Parameters:

userID - user to set preference for

itemID - item to set preference for

value - preference value

Throws:

TasteException - if an error occurs while accessing the DataModel

removePreference

public void removePreference(java.lang.Object userID,
                             java.lang.Object itemID)
                      throws TasteException

Default implementation which just calls DataModel.removePreference(Object, Object) (Object, Object)}.

Specified by:

removePreference in interface Recommender

Overrides:

removePreference in class AbstractRecommender

Parameters:

userID - user from which to remove preference

itemID - item for which to remove preference

Throws:

TasteException - if an error occurs while accessing the DataModel

refresh

public void refresh()

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.

Specified by:

refresh in interface Refreshable

Overrides:

refresh in class AbstractRecommender

toString

@NotNull
public java.lang.String toString()

Overrides:

toString in class java.lang.Object