/*
Copyright (C) 2007 Niels Ott
Copyright (C) 2007 Ramon Ziai
This file is part of Clusterlib.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
*/
package edu.isistan.uima.unified.algorithms.clustering.linkage;
import edu.isistan.uima.unified.algorithms.clustering.data.Cluster;
import edu.isistan.uima.unified.algorithms.clustering.data.DataPoint;
import edu.isistan.uima.unified.algorithms.clustering.distance.DistanceMeasure;
/**
* Nearest Neighbour Linkage (aka Single Link).
* <br> <br>
* <script type="text/javascript" src="../../../../LaTeXMathML.js"></script>
* Formula as given by
* <a href="http://www.schulteimwalde.de/phd-thesis.html">Schulte im Walde (2003, p. 186)</a>:<br>
* $d(C_i, C_j) = d_{min}(C_i, C_j) = min_{x \in C_i, y \in C_j}d(x,y)$
* @author Niels Ott
* @author Ramon Ziai
* @version $Id: NearestNeighbour.java 91 2007-07-27 11:17:28Z niels $
*/
public class NearestNeighbour implements LinkageMethod {
/**
* @see de.linuxusers.clustering.linkage.LinkageMethod#computeDistance(de.linuxusers.clustering.data.Cluster, de.linuxusers.clustering.data.Cluster)
*/
public double computeDistance(Cluster cl1, Cluster cl2, DistanceMeasure measure) {
/*
* (LOW watermark algo)
*/
double watermark = Double.MAX_VALUE;
for ( DataPoint firstPoint : cl1.getLeavesOrSelf() ) {
for ( DataPoint secondPoint : cl2.getLeavesOrSelf() ) {
// calculate (and store) distance
double distance = measure.distance(firstPoint, secondPoint);
if ( distance < watermark ) {
watermark = distance;
}
}
}
return watermark;
}
}