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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.data.spatial.SpatialComparable;
import de.lmu.ifi.dbs.elki.utilities.Alias;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
/**
* Canberra distance function, a variation of Manhattan distance.
*
* <p>
* Reference:<br />
* G. N. Lance, W. T. Williams<br />
* Computer programs for hierarchical polythetic classification ("similarity
* analysis")<br />
* In: Computer Journal, Volume 9, Issue 1
* </p>
*
* @author Erich Schubert
*/
@Reference(authors = "G. N. Lance, W. T. Williams", title = "Computer programs for hierarchical polythetic classification (similarity analysis).", booktitle = "Computer Journal, Volume 9, Issue 1", url = "http://comjnl.oxfordjournals.org/content/9/1/60.short")
@Alias({ "canberra" })
public class CanberraDistanceFunction extends AbstractSpatialDoubleDistanceFunction {
/**
* Static instance. Use this!
*/
public static final CanberraDistanceFunction STATIC = new CanberraDistanceFunction();
/**
* Constructor.
*/
protected CanberraDistanceFunction() {
super();
}
@Override
public double doubleDistance(NumberVector<?> v1, NumberVector<?> v2) {
final int dim = dimensionality(v1, v2);
double agg = 0.;
for (int d = 0; d < dim; d++) {
final double xd = v1.doubleValue(d), yd = v2.doubleValue(d);
final double div = Math.abs(xd) + Math.abs(yd);
if (div > 0) {
agg += Math.abs(xd - yd) / div;
}
}
return agg;
}
@Override
public double doubleMinDist(SpatialComparable mbr1, SpatialComparable mbr2) {
final int dim = dimensionality(mbr1, mbr2);
double agg = 0.;
for (int d = 0; d < dim; d++) {
final double diff;
if (mbr1.getMax(d) < mbr2.getMin(d)) {
diff = mbr2.getMin(d) - mbr1.getMax(d);
} else if (mbr1.getMin(d) > mbr2.getMax(d)) {
diff = mbr1.getMin(d) - mbr2.getMax(d);
} else { // The mbrs intersect!
continue;
}
final double a1 = Math.max(-mbr1.getMin(d), mbr1.getMax(d));
final double a2 = Math.max(-mbr2.getMin(d), mbr2.getMax(d));
final double div = a1 + a2;
// Cannot be 0, because then diff = 0 and we continued above.
agg += diff / div;
}
return agg;
}
@Override
public boolean isMetric() {
// As this is also reffered to as "canberra metric", it is probably a metric
// But *maybe* only for positive numbers only?
return true;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
@Override
protected CanberraDistanceFunction makeInstance() {
return CanberraDistanceFunction.STATIC;
}
}
}
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