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package de.lmu.ifi.dbs.elki.math.linearalgebra.pca;
/*
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.List;
import de.lmu.ifi.dbs.elki.logging.Logging;
import de.lmu.ifi.dbs.elki.math.linearalgebra.EigenPair;
import de.lmu.ifi.dbs.elki.math.linearalgebra.SortedEigenPairs;
import de.lmu.ifi.dbs.elki.utilities.documentation.Description;
import de.lmu.ifi.dbs.elki.utilities.documentation.Title;
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.IntParameter;
/**
* The FirstNEigenPairFilter marks the n highest eigenpairs as strong
* eigenpairs, where n is a user specified number.
*
* @author Elke Achtert
*/
// todo parameter comments
@Title("First n Eigenpair filter")
@Description("Sorts the eigenpairs in decending order of their eigenvalues and marks the first n eigenpairs as strong eigenpairs.")
public class FirstNEigenPairFilter implements EigenPairFilter {
/**
* The logger for this class.
*/
private static final Logging logger = Logging.getLogger(FirstNEigenPairFilter.class);
/**
* Paremeter n
*/
public static final OptionID EIGENPAIR_FILTER_N = OptionID.getOrCreateOptionID("pca.filter.n", "The number of strong eigenvectors: n eigenvectors with the n highest" + "eigenvalues are marked as strong eigenvectors.");
/**
* The threshold for strong eigenvectors: n eigenvectors with the n highest
* eigenvalues are marked as strong eigenvectors.
*/
private int n;
/**
* Constructor.
*
* @param n
*/
public FirstNEigenPairFilter(int n) {
super();
this.n = n;
}
@Override
public FilteredEigenPairs filter(SortedEigenPairs eigenPairs) {
StringBuffer msg = new StringBuffer();
if(logger.isDebugging()) {
msg.append("sortedEigenPairs ").append(eigenPairs.toString());
msg.append("\nn = ").append(n);
}
// init strong and weak eigenpairs
List<EigenPair> strongEigenPairs = new ArrayList<EigenPair>();
List<EigenPair> weakEigenPairs = new ArrayList<EigenPair>();
// determine strong and weak eigenpairs
for(int i = 0; i < eigenPairs.size(); i++) {
EigenPair eigenPair = eigenPairs.getEigenPair(i);
if(i < n) {
strongEigenPairs.add(eigenPair);
}
else {
weakEigenPairs.add(eigenPair);
}
}
if(logger.isDebugging()) {
msg.append("\nstrong EigenPairs = ").append(strongEigenPairs);
msg.append("\nweak EigenPairs = ").append(weakEigenPairs);
logger.debugFine(msg.toString());
}
return new FilteredEigenPairs(weakEigenPairs, strongEigenPairs);
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
/**
* The number of eigenpairs to keep.
*/
protected int n = 0;
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
IntParameter nP = new IntParameter(EIGENPAIR_FILTER_N, new GreaterEqualConstraint(0));
if(config.grab(nP)) {
n = nP.getValue();
}
}
@Override
protected FirstNEigenPairFilter makeInstance() {
return new FirstNEigenPairFilter(n);
}
}
}
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