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package de.lmu.ifi.dbs.elki.distance.distancefunction.strings;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2015
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import de.lmu.ifi.dbs.elki.data.type.SimpleTypeInformation;
import de.lmu.ifi.dbs.elki.data.type.TypeUtil;
import de.lmu.ifi.dbs.elki.distance.distancefunction.AbstractPrimitiveDistanceFunction;
import de.lmu.ifi.dbs.elki.utilities.documentation.Description;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
/**
* Levenshtein distance on strings, normalized by string length.
*
* Reference:
* <p>
* V. I. Levenshtein<br>
* Binary codes capable of correcting deletions, insertions and reversals.<br>
* Soviet physics doklady. Vol. 10. 1966.
* </p>
*
* TODO: add case insensitive flag.
*
* @author Felix Stahlberg
* @author Erich Schubert
*
* @apiviz.uses String
*/
@Description("Levenshtein distance, normalized by average string length.")
@Reference(authors = "V. I. Levenshtein", title = "Binary codes capable of correcting deletions, insertions and reversals.", booktitle = "Soviet physics doklady. Vol. 10. 1966.")
public class NormalizedLevenshteinDistanceFunction extends AbstractPrimitiveDistanceFunction<String> {
/**
* Static instance, case sensitive.
*/
public static final NormalizedLevenshteinDistanceFunction STATIC_SENSITIVE = new NormalizedLevenshteinDistanceFunction();
/**
* Constructor. Use static instance instead.
*/
@Deprecated
public NormalizedLevenshteinDistanceFunction() {
super();
}
@Override
public double distance(String o1, String o2) {
int cost = LevenshteinDistanceFunction.levenshteinDistance(o1, o2);
return cost * 2.0 / (o1.length() + o2.length());
}
@Override
public SimpleTypeInformation<? super String> getInputTypeRestriction() {
return TypeUtil.STRING;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
@Override
protected NormalizedLevenshteinDistanceFunction makeInstance() {
return STATIC_SENSITIVE;
}
}
}
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