/*
* RapidMiner
*
* Copyright (C) 2001-2008 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.com
*
* 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/.
*/
package com.rapidminer.tools.math.similarity.mixed;
import com.rapidminer.example.Attribute;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.tools.math.similarity.DistanceMeasure;
/**
* Euclidean distance for numerical and nominal values. For nomimal values, a distance of one is accounted if both values are not the same. Note: In
* most cases, you must normalize the numerical values, to obtain sound results.
*
* @author Sebastian Land, Michael Wurst
* @version $Id: MixedEuclideanDistance.java,v 1.1 2008/08/05 09:40:31 stiefelolm Exp $
*/
public class MixedEuclideanDistance extends DistanceMeasure {
private boolean[] isNominal;
public double calculateDistance(double[] value1, double[] value2) {
double sum = 0.0;
int counter = 0;
for (int i = 0; i < value1.length; i++) {
if ((!Double.isNaN(value1[i])) && (!Double.isNaN(value2[i]))) {
if (isNominal[i]) {
if (value1[i] != value1[i])
sum = sum + 1.0;
} else {
sum = sum + Math.pow(value1[i] - value2[i], 2);
}
counter++;
}
}
if (counter > 0)
return Math.sqrt(sum);
else
return Double.NaN;
}
public double calculateSimilarity(double[] value1, double[] value2) {
return -calculateDistance(value1, value2);
}
public void init(ExampleSet exampleSet) {
isNominal = new boolean[exampleSet.getAttributes().size()];
int index = 0;
for (Attribute attribute : exampleSet.getAttributes()) {
isNominal[index++] = attribute.isNominal();
}
}
}