org.apache.mahout.cf.taste.impl.neighborhood

Class ThresholdUserNeighborhood

java.lang.Object

org.apache.mahout.cf.taste.impl.neighborhood.ThresholdUserNeighborhood

All Implemented Interfaces:

Refreshable, UserNeighborhood

public final class ThresholdUserNeighborhood
extends Object

Computes a neigbhorhood consisting of all users whose similarity to the given user meets or exceeds a certain threshold. Similarity is defined by the given UserSimilarity.

Constructor Summary

Constructors

Constructor and Description
ThresholdUserNeighborhood(double threshold, UserSimilarity userSimilarity, DataModel dataModel)
ThresholdUserNeighborhood(double threshold, UserSimilarity userSimilarity, DataModel dataModel, double samplingRate)

Method Summary

Modifier and Type	Method and Description
long[]	getUserNeighborhood(long userID)
void	refresh(Collection<Refreshable> alreadyRefreshed) Triggers "refresh" -- whatever that means -- of the implementation.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ThresholdUserNeighborhood

public ThresholdUserNeighborhood(double threshold,
                                 UserSimilarity userSimilarity,
                                 DataModel dataModel)

Parameters:

threshold - similarity threshold

userSimilarity - similarity metric

dataModel - data model

Throws:

IllegalArgumentException - if threshold is Double.NaN, or if samplingRate is not positive and less than or equal to 1.0, or if userSimilarity or dataModel are null

ThresholdUserNeighborhood

public ThresholdUserNeighborhood(double threshold,
                                 UserSimilarity userSimilarity,
                                 DataModel dataModel,
                                 double samplingRate)

Parameters:

threshold - similarity threshold

userSimilarity - similarity metric

dataModel - data model

samplingRate - percentage of users to consider when building neighborhood -- decrease to trade quality for performance

Throws:

IllegalArgumentException - if threshold or samplingRate is Double.NaN, or if samplingRate is not positive and less than or equal to 1.0, or if userSimilarity or dataModel are null

Method Detail

getUserNeighborhood

public long[] getUserNeighborhood(long userID)
                           throws TasteException

Parameters:

userID - ID of user for which a neighborhood will be computed

Returns:

IDs of users in the neighborhood

Throws:

TasteException - if an error occurs while accessing data

toString

public String toString()

Overrides:

toString in class Object

refresh

public final 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.

Specified by:

refresh in interface Refreshable

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.