org.simmetrics.metrics

Class GeneralizedJaccard<T>

java.lang.Object

org.simmetrics.metrics.GeneralizedJaccard<T>

Type Parameters:

T - type of the token

All Implemented Interfaces:

Distance<com.google.common.collect.Multiset<T>>, Metric<com.google.common.collect.Multiset<T>>, MultisetDistance<T>, MultisetMetric<T>

public final class GeneralizedJaccard<T>
extends Object
implements MultisetMetric<T>, MultisetDistance<T>

Calculates the generalized Jaccard distance and similarity coefficient over two multisets. The similarity is defined as the size of the intersection divided by the size of the union of the sample sets. The distance is obtained by subtracting the Jaccard coefficient from 1.

similarity(a,b) = ∣a ∩ b∣ / ∣a ∪ b∣
distance(a,b) = 1 - similarity(a,b)

When ∣a ∪ b∣ is empty the multisets have no elements in common. In this case the similarity is 0 by definition.

Unlike the Jaccard index 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 the Jaccard index but are dissimilar when the generalized version is used.

This class is immutable and thread-safe.

See Also:

Jaccard, Wikipedia - Jaccard index

Constructor Summary

Constructors

Constructor and Description
GeneralizedJaccard()

Method Summary

Modifier and Type	Method and Description
float	compare(com.google.common.collect.Multiset<T> a, com.google.common.collect.Multiset<T> b) Measures the similarity between multisets a and b.
float	distance(com.google.common.collect.Multiset<T> a, com.google.common.collect.Multiset<T> b) Measures the distance between multisets a and b.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

GeneralizedJaccard

public GeneralizedJaccard()

Method Detail

compare

public float compare(com.google.common.collect.Multiset<T> a,
                     com.google.common.collect.Multiset<T> b)

Description copied from interface: MultisetMetric

Measures the similarity between multisets 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 a and b are based on different equivalence relations (as HashMultiset and TreeMultiset are).

Specified by:

compare in interface Metric<com.google.common.collect.Multiset<T>>

Specified by:

compare in interface MultisetMetric<T>

Parameters:

a - multisets a to compare

b - multisets b to compare

Returns:

a value between 0 and 1 inclusive indicating similarity

distance

public float distance(com.google.common.collect.Multiset<T> a,
                      com.google.common.collect.Multiset<T> b)

Description copied from interface: MultisetDistance

Measures the distance between multisets a and b. The measurement results in a non-negative value. A value of 0.0 indicates that a and b are similar.

Results are undefined if a and b are based on different equivalence relations (as HashMultiset and TreeMultiset are).

Specified by:

distance in interface Distance<com.google.common.collect.Multiset<T>>

Specified by:

distance in interface MultisetDistance<T>

Parameters:

a - list a to compare

b - list b to compare

Returns:

a non-negative value

toString

public String toString()

Overrides:

toString in class Object