org.simmetrics

Interface SetDistance<E>

Type Parameters:

E - the type of elements contained in the lists

All Superinterfaces:

Distance<Set<E>>

All Known Implementing Classes:

Dice, Jaccard, OverlapCoefficient

public interface SetDistance<E>
extends Distance<Set<E>>

Measures the unnormalized dissimilarity between two arbitrary sets containing elements of the same type. The measurement results in a non-negative value. A value of zero indicates that the objects are similar.

The elements in the sets have to implement Object.hashCode() and Object.equals(Object).

The distance measure should be consistent with equals such that a.equals(b) => distance(a,b) == 0.0.

The distance measure should be reflexive such that distance(a,a) == 0.0.

The distance measure should be symmetric such that distance(a,b) == distance(b,a).

Implementations may not modify the contents of the sets. List should be treated as if wrapped by Collections.unmodifiableSet(Set).

See Also:

Wikipedia - Metric

Method Summary

Modifier and Type	Method and Description
float	distance(Set<E> a, Set<E> b) Measures the distance between sets a and b.

Method Detail

distance

float distance(Set<E> a,
               Set<E> b)

Measures the distance between sets 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 sets based on different equivalence relations (as HashSet, TreeSet, and the keySet of an IdentityHashMap all are).

Specified by:

distance in interface Distance<Set<E>>

Parameters:

a - set a to compare

b - set b to compare

Returns:

a non-negative value

Throws:

NullPointerException - when either a or b is null