smile.math.distance

Class EditDistance

java.lang.Object

smile.math.distance.EditDistance

All Implemented Interfaces:

Distance<String>, Metric<String>

public class EditDistance
extends Object
implements Metric<String>

The Edit distance between two strings is a metric for measuring the amount of difference between two sequences. The Levenshtein distance between two strings is given by the minimum number of operations needed to transform one string into the other, where an operation is an insertion, deletion, or substitution of a single character. A generalization of the Levenshtein distance (Damerau-Levenshtein distance) allows the transposition of two characters as an operation.

Given two strings x and y of length m and n (suppose n ≥ m), this implementation takes O(ne) time and O(mn) space by an extended Ukkonen's algorithm in case of unit cost, where e is the edit distance between x and y. Thus this algorithm is output sensitive. The smaller the distance, the faster it runs.

For weighted cost, this implements the regular dynamic programming algorithm, which takes O(mn) time and O(m) space.

Author:

Haifeng Li

Constructor Summary

Constructors

Constructor and Description
EditDistance(double[][] weight) Constructor.
EditDistance(double[][] weight, double radius) Constructor.
EditDistance(int maxStringLength) Constructor.
EditDistance(int maxStringLength, boolean damerau) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
double	d(char[] x, char[] y) Edit distance between two strings.
double	d(String x, String y) Edit distance between two strings.
static int	damerau(char[] x, char[] y) Damerau-Levenshtein distance between two strings allows insertion, deletion, substitution, or transposition of characters.
static int	damerau(String x, String y) Damerau-Levenshtein distance between two strings allows insertion, deletion, substitution, or transposition of characters.
static int	levenshtein(char[] x, char[] y) Levenshtein distance between two strings allows insertion, deletion, or substitution of characters.
static int	levenshtein(String x, String y) Levenshtein distance between two strings allows insertion, deletion, or substitution of characters.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

EditDistance

public EditDistance(double[][] weight)

Constructor. Weighted Levenshtein distance without path constraints. Only insertion, deletion, and substitution operations are supported.

EditDistance

public EditDistance(double[][] weight,
            double radius)

Constructor. Weighted Levenshtein distance with Sakoe-Chiba band, which improve computational cost. Only insertion, deletion, and substitution operations are supported.

Parameters:

radius - the window width of Sakoe-Chiba band in terms of percentage of sequence length.

EditDistance

public EditDistance(int maxStringLength)

Constructor. Unit cost edit distance.

Parameters:

maxStringLength - the maximum length of strings that will be feed to this algorithm.

EditDistance

public EditDistance(int maxStringLength,
            boolean damerau)

Constructor. Damerau-Levenshtein distance.

Parameters:

maxStringLength - the maximum length of strings that will be feed to this algorithm.

damerau - if true, calculate Damerau-Levenshtein distance instead of plain Levenshtein distance.

Method Detail

toString

public String toString()

Overrides:

toString in class Object

d

public double d(String x,
       String y)

Edit distance between two strings. O(mn) time and O(n) space for weighted edit distance. O(ne) time and O(mn) space for unit cost edit distance. For weighted edit distance, this method is multi-thread safe. However, it is NOT multi-thread safe for unit cost edit distance.

Specified by:

d in interface Distance<String>

d

public double d(char[] x,
       char[] y)

Edit distance between two strings. O(mn) time and O(n) space for weighted edit distance. O(ne) time and O(mn) space for unit cost edit distance. For weighted edit distance, this method is multi-thread safe. However, it is NOT multi-thread safe for unit cost edit distance.

levenshtein

public static int levenshtein(String x,
              String y)

Levenshtein distance between two strings allows insertion, deletion, or substitution of characters. O(mn) time and O(n) space. Multi-thread safe.

levenshtein

public static int levenshtein(char[] x,
              char[] y)

Levenshtein distance between two strings allows insertion, deletion, or substitution of characters. O(mn) time and O(n) space. Multi-thread safe.

damerau

public static int damerau(String x,
          String y)

Damerau-Levenshtein distance between two strings allows insertion, deletion, substitution, or transposition of characters. O(mn) time and O(n) space. Multi-thread safe.

damerau

public static int damerau(char[] x,
          char[] y)

Damerau-Levenshtein distance between two strings allows insertion, deletion, substitution, or transposition of characters. O(mn) time and O(n) space. Multi-thread safe.