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) 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 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.GreaterEqualConstraint;
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;
/**
* Grid-based strategy to pick reference points.
*
* @author Erich Schubert
*
* @param <V> Object type
*/
public class GridBasedReferencePoints<V extends NumberVector<V, ?>> implements ReferencePointsHeuristic<V> {
// TODO: add "grid sampling" option.
/**
* Parameter to specify the grid resolution.
* <p>
* Key: {@code -grid.size}
* </p>
*/
public static final OptionID GRID_ID = OptionID.getOrCreateOptionID("grid.size", "The number of partitions in each dimension. Points will be placed on the edges of the grid, except for a grid size of 0, where only the mean is generated as reference point.");
/**
* Parameter to specify the extra scaling of the space, to allow
* out-of-data-space reference points.
* <p>
* Key: {@code -grid.oversize}
* </p>
*/
public static final OptionID GRID_SCALE_ID = OptionID.getOrCreateOptionID("grid.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 #GRID_ID}.
*/
protected int gridres;
/**
* Holds the value of {@link #GRID_SCALE_ID}.
*/
protected double gridscale;
/**
* Constructor.
*
* @param gridres
* @param gridscale
*/
public GridBasedReferencePoints(int gridres, double gridscale) {
super();
this.gridres = gridres;
this.gridscale = gridscale;
}
@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];
for(int d = 0; d < dim; d++) {
mean[d] = (minmax.first.doubleValue(d + 1) + minmax.second.doubleValue(d + 1)) / 2;
}
int gridpoints = Math.max(1, (int) Math.pow(gridres + 1, dim));
ArrayList<V> result = new ArrayList<V>(gridpoints);
double[] delta = new double[dim];
if(gridres > 0) {
double halfgrid = gridres / 2.0;
for(int d = 0; d < dim; d++) {
delta[d] = (minmax.second.doubleValue(d + 1) - minmax.first.doubleValue(d + 1)) / gridres;
}
double[] vec = new double[dim];
for(int i = 0; i < gridpoints; i++) {
int acc = i;
for(int d = 0; d < dim; d++) {
int coord = acc % (gridres + 1);
acc = acc / (gridres + 1);
vec[d] = mean[d] + (coord - halfgrid) * delta[d] * gridscale;
}
V newp = factory.newNumberVector(vec);
// logger.debug("New reference point: " + FormatUtil.format(vec));
result.add(newp);
}
}
else {
result.add(factory.newNumberVector(mean));
// logger.debug("New reference point: " + FormatUtil.format(mean));
}
return result;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer<V extends NumberVector<V, ?>> extends AbstractParameterizer {
/**
* Holds the value of {@link #GRID_ID}.
*/
protected int gridres;
/**
* Holds the value of {@link #GRID_SCALE_ID}.
*/
protected double gridscale;
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
IntParameter GRID_PARAM = new IntParameter(GRID_ID, new GreaterEqualConstraint(0), 1);
if(config.grab(GRID_PARAM)) {
gridres = GRID_PARAM.getValue();
}
DoubleParameter GRID_SCALE_PARAM = new DoubleParameter(GRID_SCALE_ID, new GreaterEqualConstraint(0.0), 1.0);
if(config.grab(GRID_SCALE_PARAM)) {
gridscale = GRID_SCALE_PARAM.getValue();
}
}
@Override
protected GridBasedReferencePoints<V> makeInstance() {
return new GridBasedReferencePoints<V>(gridres, gridscale);
}
}
}