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package de.lmu.ifi.dbs.elki.distance.distancefunction;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2011
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.NumberVector;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
/**
* Cosine distance function for feature vectors.
*
* The cosine distance is computed as the arcus from the cosine similarity
* value, i.e., <code>arccos(<v1,v2>)</code>.
*
* @author Arthur Zimek
*/
public class ArcCosineDistanceFunction extends AbstractCosineDistanceFunction {
/**
* Static instance
*/
public static final ArcCosineDistanceFunction STATIC = new ArcCosineDistanceFunction();
/**
* Provides a CosineDistanceFunction.
*
* @deprecated Use static instance!
*/
@Deprecated
public ArcCosineDistanceFunction() {
super();
}
/**
* Computes the cosine distance for two given feature vectors.
*
* The cosine distance is computed as the arcus from the cosine similarity
* value, i.e., <code>arccos(<v1,v2>)</code>.
*
* @param v1 first feature vector
* @param v2 second feature vector
* @return the cosine distance for two given feature vectors v1 and v2
*/
@Override
public double doubleDistance(NumberVector<?,?> v1, NumberVector<?,?> v2) {
double d = Math.acos(angle(v1, v2));
if(d < 0) {
d = 0;
}
return d;
}
@Override
public String toString() {
return "ArcCosineDistance";
}
@Override
public boolean equals(Object obj) {
if(obj == null) {
return false;
}
if(obj == this) {
return true;
}
return this.getClass().equals(obj.getClass());
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
@Override
protected ArcCosineDistanceFunction makeInstance() {
return ArcCosineDistanceFunction.STATIC;
}
}
}
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