org.apache.mahout.cf.taste.similarity

Interface UserSimilarity

All Superinterfaces:

Refreshable

All Known Implementing Classes:

CachingUserSimilarity, CityBlockSimilarity, EuclideanDistanceSimilarity, GenericUserSimilarity, LogLikelihoodSimilarity, PearsonCorrelationSimilarity, SpearmanCorrelationSimilarity, TanimotoCoefficientSimilarity, UncenteredCosineSimilarity

public interface UserSimilarity
extends Refreshable

Implementations of this interface define a notion of similarity between two users. Implementations should return values in the range -1.0 to 1.0, with 1.0 representing perfect similarity.

See Also:

ItemSimilarity

Method Summary

Modifier and Type	Method and Description
void	setPreferenceInferrer(PreferenceInferrer inferrer) Attaches a PreferenceInferrer to the UserSimilarity implementation.
double	userSimilarity(long userID1, long userID2) Returns the degree of similarity, of two users, based on the their preferences.

Methods inherited from interface org.apache.mahout.cf.taste.common.Refreshable

refresh

Method Detail

userSimilarity

double userSimilarity(long userID1,
                      long userID2)
               throws TasteException

Returns the degree of similarity, of two users, based on the their preferences.

Parameters:

userID1 - first user ID

userID2 - second user ID

Returns:

similarity between the users, in [-1,1] or Double.NaN similarity is unknown

Throws:

NoSuchUserException - if either user is known to be non-existent in the data

TasteException - if an error occurs while accessing the data

setPreferenceInferrer

void setPreferenceInferrer(PreferenceInferrer inferrer)

Attaches a PreferenceInferrer to the UserSimilarity implementation.

Parameters:

inferrer - PreferenceInferrer