package de.lmu.ifi.dbs.elki.distance.similarityfunction;
/*
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 de.lmu.ifi.dbs.elki.data.type.SimpleTypeInformation;
import de.lmu.ifi.dbs.elki.distance.distancefunction.PrimitiveDistanceFunction;
import de.lmu.ifi.dbs.elki.distance.distancevalue.DoubleDistance;
import de.lmu.ifi.dbs.elki.distance.distancevalue.NumberDistance;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.OptionID;
/**
* Adapter to use a primitive number-distance as similarity measure, by computing
* 1/distance.
*
* @author Erich Schubert
*
* @param <O> Object type
*/
public class InvertedDistanceSimilarityFunction<O> extends AbstractPrimitiveSimilarityFunction<O, DoubleDistance> {
/**
* Parameter to specify the similarity function to derive the distance between
* database objects from. Must extend
* {@link de.lmu.ifi.dbs.elki.distance.distancefunction.DistanceFunction} .
* <p>
* Key: {@code -adapter.distancefunction}
* </p>
* <p>
* Default value:
* {@link de.lmu.ifi.dbs.elki.distance.distancefunction.EuclideanDistanceFunction}
* </p>
*/
public static final OptionID DISTANCE_FUNCTION_ID = OptionID.getOrCreateOptionID("adapter.distancefunction", "Distance function to derive the similarity between database objects from.");
/**
* Holds the similarity function.
*/
protected PrimitiveDistanceFunction<? super O, ? extends NumberDistance<?, ?>> distanceFunction;
@Override
public DoubleDistance getDistanceFactory() {
return DoubleDistance.FACTORY;
}
@Override
public SimpleTypeInformation<? super O> getInputTypeRestriction() {
return distanceFunction.getInputTypeRestriction();
}
@Override
public DoubleDistance similarity(O o1, O o2) {
double dist = distanceFunction.distance(o1, o2).doubleValue();
return new DoubleDistance(1. / dist);
}
}