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) 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 java.util.ArrayList;
import java.util.Collection;
import de.lmu.ifi.dbs.elki.data.NumberVector;
import de.lmu.ifi.dbs.elki.database.relation.Relation;
import de.lmu.ifi.dbs.elki.utilities.DatabaseUtil;
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.GreaterConstraint;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameterization.Parameterization;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.DoubleParameter;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.IntParameter;
import de.lmu.ifi.dbs.elki.utilities.pairs.Pair;
/**
* Reference points generated randomly within the used data space.
*
* @author Erich Schubert
*
* @param <V> Object type
*/
// TODO: Erich: use reproducible random
public class RandomGeneratedReferencePoints<V extends NumberVector<V, ?>> implements ReferencePointsHeuristic<V> {
/**
* Parameter to specify the number of requested reference points.
* <p>
* Key: {@code -generate.n}
* </p>
*/
public static final OptionID N_ID = OptionID.getOrCreateOptionID("generate.n", "The number of reference points to be generated.");
/**
* Parameter for additional scaling of the space, to allow out-of-space
* reference points.
* <p>
* Key: {@code -generate.scale}
* </p>
*/
public static final OptionID SCALE_ID = OptionID.getOrCreateOptionID("generate.scale", "Scale the grid by the given factor. This can be used to obtain reference points outside the used data space.");
/**
* Holds the value of {@link #N_ID}.
*/
protected int samplesize;
/**
* Holds the value of {@link #SCALE_ID}.
*/
protected double scale = 1.0;
/**
* Constructor.
*
* @param samplesize
* @param scale
*/
public RandomGeneratedReferencePoints(int samplesize, double scale) {
super();
this.samplesize = samplesize;
this.scale = scale;
}
@Override
public <T extends V> Collection<V> getReferencePoints(Relation<T> db) {
Relation<V> database = DatabaseUtil.relationUglyVectorCast(db);
Pair<V, V> minmax = DatabaseUtil.computeMinMax(database);
V factory = DatabaseUtil.assumeVectorField(database).getFactory();
int dim = DatabaseUtil.dimensionality(db);
// Compute mean from minmax.
double[] mean = new double[dim];
double[] delta = new double[dim];
for(int d = 0; d < dim; d++) {
mean[d] = (minmax.first.doubleValue(d + 1) + minmax.second.doubleValue(d + 1)) / 2;
delta[d] = (minmax.second.doubleValue(d + 1) - minmax.first.doubleValue(d + 1));
}
ArrayList<V> result = new ArrayList<V>(samplesize);
double[] vec = new double[dim];
for(int i = 0; i < samplesize; i++) {
for(int d = 0; d < dim; d++) {
vec[d] = mean[d] + (Math.random() - 0.5) * scale * delta[d];
}
V newp = factory.newInstance(vec);
// logger.debug("New reference point: " + FormatUtil.format(vec));
result.add(newp);
}
return result;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer<V extends NumberVector<V, ?>> extends AbstractParameterizer {
/**
* Holds the value of {@link #N_ID}.
*/
protected int samplesize;
/**
* Holds the value of {@link #SCALE_ID}.
*/
protected double scale = 1.0;
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
IntParameter samplesizeP = new IntParameter(N_ID, new GreaterConstraint(0));
if(config.grab(samplesizeP)) {
samplesize = samplesizeP.getValue();
}
DoubleParameter scaleP = new DoubleParameter(SCALE_ID, new GreaterConstraint(0.0), 1.0);
if(config.grab(scaleP)) {
scale = scaleP.getValue();
}
}
@Override
protected RandomGeneratedReferencePoints<V> makeInstance() {
return new RandomGeneratedReferencePoints<V>(samplesize, scale);
}
}
}