org.simmetrics.metrics

Class TanimotoCoefficient<T>

java.lang.Object

org.simmetrics.metrics.TanimotoCoefficient<T>

Type Parameters:

T - type of the token

All Implemented Interfaces:

Metric<Set<T>>, SetMetric<T>

public final class TanimotoCoefficient<T>
extends Object
implements SetMetric<T>

Calculates the Tanimoto similarity coefficient over two sets. The similarity is defined as the cosine of the angle between the sets expressed as sparse vectors.

similarity(a,b) = a·b / (||a|| * ||b||)

The cosine similarity is identical to the Tanimoto coefficient, but unlike Tanimoto the occurrence (cardinality) of an entry is taken into account. E.g. [hello, world] and [hello, world, hello, world] would be identical when compared with Tanimoto but are dissimilar when the cosine similarity is used.

This class is immutable and thread-safe.

See Also:

CosineSimilarity, Wikipedia Cosine similarity

Constructor Summary

Constructors

Constructor and Description
TanimotoCoefficient()

Method Summary

Modifier and Type	Method and Description
float	compare(Set<T> a, Set<T> b) Measures the similarity between sets a and b.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

TanimotoCoefficient

public TanimotoCoefficient()

Method Detail

compare

public float compare(Set<T> a,
                     Set<T> b)

Description copied from interface: SetMetric

Measures the similarity between sets a and b. The measurement results in a value between 0 and 1 inclusive. A value of zero indicates that the sets are dissimilar, a value of 1 indicates they are similar.

Results are undefined if set1 and set2 are sets based on different equivalence relations (as HashSet, TreeSet, and the keySet of an IdentityHashMap all are).

Specified by:

compare in interface Metric<Set<T>>

Specified by:

compare in interface SetMetric<T>

Parameters:

a - set a to compare

b - set b to compare

Returns:

a value between 0 and 1 inclusive indicating similarity

toString

public String toString()

Overrides:

toString in class Object