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package de.lmu.ifi.dbs.elki.math.linearalgebra;
/*
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.Arrays;
import java.util.Comparator;
import java.util.List;
/**
* Helper class which encapsulates an array of eigenpairs (i.e. an array of
* eigenvectors and their corresponding eigenvalues). This class is used to sort
* eigenvectors (and -values).
*
* @author Elke Achtert
*
* @apiviz.composedOf de.lmu.ifi.dbs.elki.math.linearalgebra.EigenPair
*/
public class SortedEigenPairs {
/**
* The array of eigenpairs.
*/
private EigenPair[] eigenPairs;
/**
* Creates a new empty SortedEigenPairs object. Can only be called from the
* copy() method.
*/
private SortedEigenPairs() {
// nothing to do here.
}
/**
* Creates a new SortedEigenPairs object from the specified eigenvalue
* decomposition. The eigenvectors are sorted according to the specified
* order.
*
* @param evd the underlying eigenvalue decomposition
* @param ascending a boolean that indicates ascending order
*/
public SortedEigenPairs(EigenvalueDecomposition evd, final boolean ascending) {
double[] eigenvalues = evd.getRealEigenvalues();
Matrix eigenvectors = evd.getV();
this.eigenPairs = new EigenPair[eigenvalues.length];
for(int i = 0; i < eigenvalues.length; i++) {
double e = java.lang.Math.abs(eigenvalues[i]);
Vector v = eigenvectors.getColumnVector(i);
eigenPairs[i] = new EigenPair(v, e);
}
Comparator<EigenPair> comp = new Comparator<EigenPair>() {
@Override
public int compare(EigenPair o1, EigenPair o2) {
int comp = o1.compareTo(o2);
if(!ascending) {
comp = -1 * comp;
}
return comp;
}
};
Arrays.sort(eigenPairs, comp);
}
/**
* Creates a new SortedEigenPairs object from the specified list. The
* eigenvectors are sorted in descending order.
*
* @param eigenPairs the eigenpairs to be sorted
*/
public SortedEigenPairs(List<EigenPair> eigenPairs) {
Comparator<EigenPair> comp = new Comparator<EigenPair>() {
@Override
public int compare(EigenPair o1, EigenPair o2) {
return -1 * o1.compareTo(o2);
}
};
this.eigenPairs = eigenPairs.toArray(new EigenPair[eigenPairs.size()]);
Arrays.sort(this.eigenPairs, comp);
}
/**
* Returns the sorted eigenvalues.
*
* @return the sorted eigenvalues
*/
public double[] eigenValues() {
double[] eigenValues = new double[eigenPairs.length];
for(int i = 0; i < eigenPairs.length; i++) {
EigenPair eigenPair = eigenPairs[i];
eigenValues[i] = eigenPair.getEigenvalue();
}
return eigenValues;
}
/**
* Returns the sorted eigenvectors.
*
* @return the sorted eigenvectors
*/
public Matrix eigenVectors() {
Matrix eigenVectors = new Matrix(eigenPairs.length, eigenPairs.length);
for(int i = 0; i < eigenPairs.length; i++) {
EigenPair eigenPair = eigenPairs[i];
eigenVectors.setColumnVector(i, eigenPair.getEigenvector());
}
return eigenVectors;
}
/**
* Returns the first <code>n</code> sorted eigenvectors as a matrix.
*
* @param n the number of eigenvectors (columns) to be returned
* @return the first <code>n</code> sorted eigenvectors
*/
public Matrix eigenVectors(int n) {
Matrix eigenVectors = new Matrix(eigenPairs.length, n);
for(int i = 0; i < n; i++) {
EigenPair eigenPair = eigenPairs[i];
eigenVectors.setColumnVector(i, eigenPair.getEigenvector());
}
return eigenVectors;
}
/**
* Returns the last <code>n</code> sorted eigenvectors as a matrix.
*
* @param n the number of eigenvectors (columns) to be returned
* @return the last <code>n</code> sorted eigenvectors
*/
public Matrix reverseEigenVectors(int n) {
Matrix eigenVectors = new Matrix(eigenPairs.length, n);
for(int i = 0; i < n; i++) {
EigenPair eigenPair = eigenPairs[eigenPairs.length - 1 - i];
eigenVectors.setColumnVector(i, eigenPair.getEigenvector());
}
return eigenVectors;
}
/**
* Returns the eigenpair at the specified index.
*
* @param index the index of the eigenpair to be returned
* @return the eigenpair at the specified index
*/
public EigenPair getEigenPair(int index) {
return eigenPairs[index];
}
/**
* Returns the number of the eigenpairs.
*
* @return the number of the eigenpairs
*/
public int size() {
return eigenPairs.length;
}
/**
* Returns a string representation of this EigenPair.
*
* @return a string representation of this EigenPair
*/
@Override
public String toString() {
StringBuffer result = new StringBuffer();
for(EigenPair eigenPair : eigenPairs) {
result.append("\n").append(eigenPair);
}
return result.toString();
}
/**
* Returns a deep copy of this object
*
* @return new copy
*/
public SortedEigenPairs copy() {
SortedEigenPairs cp = new SortedEigenPairs();
cp.eigenPairs = this.eigenPairs.clone();
return cp;
}
}
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