org.grouplens.lenskit.vectors.similarity

Class CosineVectorSimilarity

java.lang.Object

org.grouplens.lenskit.vectors.similarity.CosineVectorSimilarity

All Implemented Interfaces:

Serializable, VectorSimilarity

@Shareable
public class CosineVectorSimilarity
extends Object
implements VectorSimilarity, Serializable

Cosine similarity for vectors.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
CosineVectorSimilarity() Construct an undamped cosine similarity function.
CosineVectorSimilarity(double damping) Construct a new cosine similarity function.

Method Summary

Modifier and Type	Method and Description
boolean	isSparse() Query whether this similarity function is sparse (returns 0 for vectors with disjoint key sets).
boolean	isSymmetric() Query whether this similarity function is symmetric.
double	similarity(SparseVector vec1, SparseVector vec2) Compute the similarity between two vectors.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

CosineVectorSimilarity

public CosineVectorSimilarity()

Construct an undamped cosine similarity function.

CosineVectorSimilarity

@Inject
public CosineVectorSimilarity(@SimilarityDamping
                                      double damping)

Construct a new cosine similarity function.

Parameters:

damping - The Bayesian damping term (added to denominator), to bias the similarity towards 0 for low-cooccurance vectors.

Method Detail

similarity

public double similarity(SparseVector vec1,
                         SparseVector vec2)

Description copied from interface: VectorSimilarity

Compute the similarity between two vectors.

Specified by:

similarity in interface VectorSimilarity

Parameters:

vec1 - The left vector to compare.

vec2 - The right vector to compare.

Returns:

The similarity, in the range [-1,1].

isSparse

public boolean isSparse()

Description copied from interface: VectorSimilarity

Query whether this similarity function is sparse (returns 0 for vectors with disjoint key sets).

Specified by:

isSparse in interface VectorSimilarity

Returns:

true iff VectorSimilarity.similarity(SparseVector, SparseVector) will always return true when applied to two vectors with no keys in common.

isSymmetric

public boolean isSymmetric()

Description copied from interface: VectorSimilarity

Query whether this similarity function is symmetric. Symmetric similarity functions return the same result when called on (A,B) and (B,A).

Specified by:

isSymmetric in interface VectorSimilarity

Returns:

true if the function is symmetric.

toString

public String toString()

Overrides:

toString in class Object