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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) 2013
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.WrongParameterValueException;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.constraints.CommonConstraints;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.constraints.GlobalParameterConstraint;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.constraints.ParameterConstraint;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.constraints.ParameterFlagGlobalConstraint;
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.Flag;
/**
* The LimitEigenPairFilter marks all eigenpairs having an (absolute) eigenvalue
* below the specified threshold (relative or absolute) as weak eigenpairs, the
* others are marked as strong eigenpairs.
*
* @author Elke Achtert
*/
@Title("Limit-based Eigenpair Filter")
@Description("Filters all eigenpairs, which are lower than a given value.")
public class LimitEigenPairFilter implements EigenPairFilter {
/**
* The logger for this class.
*/
private static final Logging LOG = Logging.getLogger(LimitEigenPairFilter.class);
/**
* "absolute" Flag
*/
public static final OptionID EIGENPAIR_FILTER_ABSOLUTE = new OptionID("pca.filter.absolute", "Flag to mark delta as an absolute value.");
/**
* Parameter delta
*/
public static final OptionID EIGENPAIR_FILTER_DELTA = new OptionID("pca.filter.delta", "The threshold for strong Eigenvalues. If not otherwise specified, delta " + "is a relative value w.r.t. the (absolute) highest Eigenvalues and has to be " + "a double between 0 and 1. To mark delta as an absolute value, use " + "the option -" + EIGENPAIR_FILTER_ABSOLUTE.getName() + ".");
/**
* The default value for delta.
*/
public static final double DEFAULT_DELTA = 0.01;
/**
* Threshold for strong eigenpairs, can be absolute or relative.
*/
private double delta;
/**
* Indicates whether delta is an absolute or a relative value.
*/
private boolean absolute;
/**
* Constructor.
*
* @param delta
* @param absolute
*/
public LimitEigenPairFilter(double delta, boolean absolute) {
super();
this.delta = delta;
this.absolute = absolute;
}
@Override
public FilteredEigenPairs filter(SortedEigenPairs eigenPairs) {
StringBuilder msg = new StringBuilder();
if(LOG.isDebugging()) {
msg.append("delta = ").append(delta);
}
// determine limit
double limit;
if(absolute) {
limit = delta;
}
else {
double max = Double.NEGATIVE_INFINITY;
for(int i = 0; i < eigenPairs.size(); i++) {
EigenPair eigenPair = eigenPairs.getEigenPair(i);
double eigenValue = Math.abs(eigenPair.getEigenvalue());
if(max < eigenValue) {
max = eigenValue;
}
}
limit = max * delta;
}
if(LOG.isDebugging()) {
msg.append("\nlimit = ").append(limit);
}
// init strong and weak eigenpairs
List<EigenPair> strongEigenPairs = new ArrayList<>();
List<EigenPair> weakEigenPairs = new ArrayList<>();
// determine strong and weak eigenpairs
for(int i = 0; i < eigenPairs.size(); i++) {
EigenPair eigenPair = eigenPairs.getEigenPair(i);
double eigenValue = Math.abs(eigenPair.getEigenvalue());
if(eigenValue >= limit) {
strongEigenPairs.add(eigenPair);
}
else {
weakEigenPairs.add(eigenPair);
}
}
if(LOG.isDebugging()) {
msg.append("\nstrong EigenPairs = ").append(strongEigenPairs);
msg.append("\nweak EigenPairs = ").append(weakEigenPairs);
LOG.debugFine(msg.toString());
}
return new FilteredEigenPairs(weakEigenPairs, strongEigenPairs);
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
/**
* Threshold for strong eigenpairs, can be absolute or relative.
*/
private double delta;
/**
* Indicates whether delta is an absolute or a relative value.
*/
private boolean absolute;
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
Flag absoluteF = new Flag(EIGENPAIR_FILTER_ABSOLUTE);
if(config.grab(absoluteF)) {
absolute = absoluteF.isTrue();
}
DoubleParameter deltaP = new DoubleParameter(EIGENPAIR_FILTER_DELTA, DEFAULT_DELTA);
deltaP.addConstraint(CommonConstraints.GREATER_EQUAL_ZERO_DOUBLE);
if(config.grab(deltaP)) {
delta = deltaP.doubleValue();
// TODO: make this a global constraint?
if(absolute && deltaP.tookDefaultValue()) {
config.reportError(new WrongParameterValueException("Illegal parameter setting: " + "Flag " + absoluteF.getName() + " is set, " + "but no value for " + deltaP.getName() + " is specified."));
}
}
// Conditional Constraint:
// delta must be >= 0 and <= 1 if it's a relative value
// Since relative or absolute is dependent on the absolute flag this is a
// global constraint!
List<ParameterConstraint<? super Double>> cons = new ArrayList<>();
// TODO: Keep the constraint here - applies to non-conditional case as
// well, and is set above.
cons.add(CommonConstraints.GREATER_EQUAL_ZERO_DOUBLE);
cons.add(CommonConstraints.LESS_EQUAL_ONE_DOUBLE);
GlobalParameterConstraint gpc = new ParameterFlagGlobalConstraint<>(deltaP, cons, absoluteF, false);
config.checkConstraint(gpc);
}
@Override
protected LimitEigenPairFilter makeInstance() {
return new LimitEigenPairFilter(delta, absolute);
}
}
}
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