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package de.lmu.ifi.dbs.elki.distance.distancefunction.correlation;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2012
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 java.util.Arrays;
import de.lmu.ifi.dbs.elki.data.NumberVector;
import de.lmu.ifi.dbs.elki.distance.distancefunction.AbstractVectorDoubleDistanceFunction;
import de.lmu.ifi.dbs.elki.math.MathUtil;
/**
* Pearson correlation distance function for feature vectors.
*
* The Pearson correlation distance is computed from the Pearson correlation
* coefficient <code>r</code> as: <code>1-r</code>. Hence, possible values of
* this distance are between 0 and 2.
*
* The distance between two vectors will be low (near 0), if their attribute
* values are dimension-wise strictly positively correlated, it will be high
* (near 2), if their attribute values are dimension-wise strictly negatively
* correlated. For Features with uncorrelated attributes, the distance value
* will be intermediate (around 1).
*
* This variation is for weighted dimensions.
*
* @author Arthur Zimek
* @author Erich Schubert
*/
public class WeightedPearsonCorrelationDistanceFunction extends AbstractVectorDoubleDistanceFunction {
/**
* Weights
*/
private double[] weights;
/**
* Provides a PearsonCorrelationDistanceFunction.
*
* @param weights Weights
*/
public WeightedPearsonCorrelationDistanceFunction(double[] weights) {
super();
this.weights = weights;
}
/**
* Computes the Pearson correlation distance for two given feature vectors.
*
* The Pearson correlation distance is computed from the Pearson correlation
* coefficient <code>r</code> as: <code>1-r</code>. Hence, possible values of
* this distance are between 0 and 2.
*
* @param v1 first feature vector
* @param v2 second feature vector
* @return the Pearson correlation distance for two given feature vectors v1
* and v2
*/
@Override
public double doubleDistance(NumberVector<?> v1, NumberVector<?> v2) {
return 1 - MathUtil.weightedPearsonCorrelationCoefficient(v1, v2, weights);
}
@Override
public boolean equals(Object obj) {
if(this == obj) {
return true;
}
if(obj == null) {
return false;
}
if (!this.getClass().equals(obj.getClass())) {
return false;
}
return Arrays.equals(this.weights, ((WeightedPearsonCorrelationDistanceFunction)obj).weights);
}
}
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