es.upm.etsisi.cf4j.recommender.knn.userSimilarityMetric

Class UserSimilarityMetric

java.lang.Object

es.upm.etsisi.cf4j.recommender.knn.userSimilarityMetric.UserSimilarityMetric

All Implemented Interfaces:

Partible<User>

Direct Known Subclasses:

AdjustedCosine, CJMSD, Correlation, CorrelationConstrained, Cosine, Jaccard, JMSD, MSD, PIP, Singularities, SpearmanRank

public abstract class UserSimilarityMetric
extends Object
implements Partible<User>

This class process the similarity measure between two users. To define your own similarity metric implementation, you must extend this class and overrides the method similarity(User user, User otherUser).

When the execution of the similarity metric is completed, the similarity of each user with respect to another one can be retrieved using the getSimilarities(int userIndex) method.

Field Summary

Fields

Modifier and Type	Field and Description
protected DataModel	datamodel DataModel for which de similarities must be computed
protected double[][]	similarities Matrix that contains the similarity between each pair of users

Constructor Summary

Constructors

Constructor and Description
UserSimilarityMetric()

Method Summary

Modifier and Type	Method and Description
void	afterRun() Is executed once after execute the method exec.
void	beforeRun() Is executed once before execute the method 'exec'.
double[]	getSimilarities(int userIndex) Returns the similarity array of an user.
void	run(User user) Is executed once for each object in the array of objects passed as parameter in the exec method of the Parallelizer class.
void	setDatamodel(DataModel datamodel) Sets the DataModel for which the similarity are going to be computed
abstract double	similarity(User user, User otherUser) This method must returns the similarity between two users.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

datamodel

protected DataModel datamodel

DataModel for which de similarities must be computed

similarities

protected double[][] similarities

Matrix that contains the similarity between each pair of users

Constructor Detail

UserSimilarityMetric

public UserSimilarityMetric()

Method Detail

setDatamodel

public void setDatamodel(DataModel datamodel)

Sets the DataModel for which the similarity are going to be computed

Parameters:

datamodel - DataModel instance

getSimilarities

public double[] getSimilarities(int userIndex)

Returns the similarity array of an user. Each position of the array contains the similarity of the user with the corresponding user at the same position in the array of Users of the DataModel instance.

Parameters:

userIndex - Index of the user

Returns:

Similarity of an user with other users of the DataModel instance

similarity

public abstract double similarity(User user,
                                  User otherUser)

This method must returns the similarity between two users.

If two users do not have a similarity value, the method must return Double.NEGATIVE_INFINITY.

The value returned by this method should be higher the greater the similarity between users.

Parameters:

user - A user

otherUser - Other user

Returns:

Similarity between user and otherUser

beforeRun

public void beforeRun()

Description copied from interface: Partible

Is executed once before execute the method 'exec'. It can be used to initialize resources.

Specified by:

beforeRun in interface Partible<User>

run

public void run(User user)

Description copied from interface: Partible

Is executed once for each object in the array of objects passed as parameter in the exec method of the Parallelizer class. These executions are performed in a parallel way. Race conditions must be handle by the developer. This method is no thread safe.

Specified by:

run in interface Partible<User>

Parameters:

user - Index of the test element.

afterRun

public void afterRun()

Description copied from interface: Partible

Is executed once after execute the method exec. It can be used to close resources.

Specified by:

afterRun in interface Partible<User>

toString

public String toString()

Overrides:

toString in class Object