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package de.lmu.ifi.dbs.elki.utilities.referencepoints;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2015
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.ArrayList;
import java.util.Collection;
import de.lmu.ifi.dbs.elki.data.NumberVector;
import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;
import de.lmu.ifi.dbs.elki.database.ids.DBIDs;
import de.lmu.ifi.dbs.elki.database.relation.Relation;
import de.lmu.ifi.dbs.elki.database.relation.RelationUtil;
import de.lmu.ifi.dbs.elki.logging.LoggingUtil;
import de.lmu.ifi.dbs.elki.math.random.RandomFactory;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.OptionID;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.constraints.CommonConstraints;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameterization.Parameterization;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.IntParameter;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.RandomParameter;
/**
* Random-Sampling strategy for picking reference points.
*
* @author Erich Schubert
*/
public class RandomSampleReferencePoints implements ReferencePointsHeuristic {
/**
* Sample size.
*/
protected int samplesize;
/**
* Random generator.
*/
protected RandomFactory rnd;
/**
* Constructor.
*
* @param samplesize Sampling size
*/
public RandomSampleReferencePoints(int samplesize, RandomFactory rnd) {
super();
this.samplesize = samplesize;
this.rnd = rnd;
}
@Override
public Collection<? extends NumberVector> getReferencePoints(Relation<? extends NumberVector> db) {
if(samplesize >= db.size()) {
LoggingUtil.warning("Requested sample size is larger than database size!");
return new RelationUtil.CollectionFromRelation<>(db);
}
DBIDs sample = DBIDUtil.randomSample(db.getDBIDs(), samplesize, rnd);
ArrayList<NumberVector> result = new ArrayList<>(sample.size());
for(DBIDIter it = sample.iter(); it.valid(); it.advance()) {
result.add(db.get(it));
}
return result;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
/**
* Parameter to specify the sample size.
* <p>
* Key: {@code -sample.n}
* </p>
*/
public static final OptionID N_ID = new OptionID("sample.n", "The number of samples to draw.");
/**
* Parameter to specify the sample size.
* <p>
* Key: {@code -sample.random}
* </p>
*/
public static final OptionID RANDOM_ID = new OptionID("sample.random", "Random generator seed.");
/**
* Sample size.
*/
protected int samplesize;
/**
* Random generator.
*/
protected RandomFactory rnd;
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
IntParameter samplesizeP = new IntParameter(N_ID)//
.addConstraint(CommonConstraints.GREATER_EQUAL_ONE_INT);
if(config.grab(samplesizeP)) {
samplesize = samplesizeP.intValue();
}
RandomParameter randomP = new RandomParameter(RANDOM_ID);
if(config.grab(randomP)) {
rnd = randomP.getValue();
}
}
@Override
protected RandomSampleReferencePoints makeInstance() {
return new RandomSampleReferencePoints(samplesize, rnd);
}
}
}
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