info.debatty.java.stringsimilarity

Class QGram

java.lang.Object

info.debatty.java.stringsimilarity.QGram

All Implemented Interfaces:

StringSimilarityInterface

public class QGram
extends Object
implements StringSimilarityInterface

Q-gram similarity and distance. Defined by Ukkonen in "Approximate string-matching with q-grams and maximal matches", http://www.sciencedirect.com/science/article/pii/0304397592901434 The distance between two strings is defined as the L1 norm of the difference of their profiles (the number of occurences of each k-shingle). Q-gram distance is a lower bound on Levenshtein distance, but can be computed in O(|A| + |B|), where Levenshtein requires O(|A|.|B|)

Author:

Thibault Debatty

Constructor Summary

Constructors

Constructor and Description
QGram()
QGram(int n)

Method Summary

Methods

Modifier and Type	Method and Description
int	absoluteDistance(String s1, String s2)
protected double	dist(String s1, String s2, boolean abs)
double	distance(String s1, String s2) Generally, distance = 1 - similarity.
static void	main(String[] args)
double	similarity(String s1, String s2)

Methods inherited from class java.lang.Object

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

Constructor Detail

QGram

public QGram(int n)

QGram

public QGram()

Method Detail

main

public static void main(String[] args)

similarity

public double similarity(String s1,
                String s2)

Specified by:

similarity in interface StringSimilarityInterface

Returns:

similarity between 0 (completely different) and 1 (s1 = s2)

distance

public double distance(String s1,
              String s2)

Description copied from interface: StringSimilarityInterface

Generally, distance = 1 - similarity. Some implementations can also provide a method distanceAbsolute

Specified by:

distance in interface StringSimilarityInterface

Returns:

distance between 0 (s1 = s2) and 1 (completely different)

absoluteDistance

public int absoluteDistance(String s1,
                   String s2)

dist

protected double dist(String s1,
          String s2,
          boolean abs)