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

Class NearestNUserNeighborhood

java.lang.Object

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

All Implemented Interfaces:

Refreshable, UserNeighborhood

public final class NearestNUserNeighborhood
extends Object

Computes a neighborhood consisting of the nearest n users to a given user. "Nearest" is defined by the given UserSimilarity.

Constructor Summary

Constructors

Constructor and Description
NearestNUserNeighborhood(int n, double minSimilarity, UserSimilarity userSimilarity, DataModel dataModel)
NearestNUserNeighborhood(int n, double minSimilarity, UserSimilarity userSimilarity, DataModel dataModel, double samplingRate)
NearestNUserNeighborhood(int n, UserSimilarity userSimilarity, DataModel dataModel)

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

NearestNUserNeighborhood

public NearestNUserNeighborhood(int n,
                                UserSimilarity userSimilarity,
                                DataModel dataModel)
                         throws TasteException

Parameters:

n - neighborhood size; capped at the number of users in the data model

Throws:

IllegalArgumentException - if n < 1, or userSimilarity or dataModel are null

TasteException

NearestNUserNeighborhood

public NearestNUserNeighborhood(int n,
                                double minSimilarity,
                                UserSimilarity userSimilarity,
                                DataModel dataModel)
                         throws TasteException

Parameters:

n - neighborhood size; capped at the number of users in the data model

minSimilarity - minimal similarity required for neighbors

Throws:

IllegalArgumentException - if n < 1, or userSimilarity or dataModel are null

TasteException

NearestNUserNeighborhood

public NearestNUserNeighborhood(int n,
                                double minSimilarity,
                                UserSimilarity userSimilarity,
                                DataModel dataModel,
                                double samplingRate)
                         throws TasteException

Parameters:

n - neighborhood size; capped at the number of users in the data model

minSimilarity - minimal similarity required for neighbors

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

Throws:

IllegalArgumentException - if n < 1 or samplingRate is NaN or not in (0,1], or userSimilarity or dataModel are null

TasteException

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.