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package de.lmu.ifi.dbs.elki.distance.distancefunction.timeseries;
/*
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 de.lmu.ifi.dbs.elki.data.NumberVector;
import de.lmu.ifi.dbs.elki.distance.distancevalue.DoubleDistance;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
import de.lmu.ifi.dbs.elki.utilities.documentation.Title;
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;
/**
* Provides the Edit Distance With Real Penalty distance for FeatureVectors.
*
* @author Thomas Bernecker
*/
@Title("Edit Distance with Real Penalty")
@Reference(authors = "L. Chen and R. Ng", title = "On the marriage of Lp-norms and edit distance", booktitle = "VLDB '04: Proceedings of the Thirtieth international conference on Very large data bases", url = "http://www.vldb.org/conf/2004/RS21P2.PDF")
public class ERPDistanceFunction extends AbstractEditDistanceFunction {
/**
* G parameter
*/
public static final OptionID G_ID = OptionID.getOrCreateOptionID("erp.g", "the g parameter ERP (positive number)");
/**
* Keeps the currently set g.
*/
private double g;
/**
* Constructor.
*
* @param bandSize Band size
* @param g G parameter
*/
public ERPDistanceFunction(double bandSize, double g) {
super(bandSize);
this.g = g;
}
/**
* Provides the Edit Distance With Real Penalty distance between the given two
* vectors.
*
* @return the Edit Distance With Real Penalty distance between the given two
* vectors as an instance of {@link DoubleDistance DoubleDistance}.
*/
@Override
public double doubleDistance(NumberVector<?, ?> v1, NumberVector<?, ?> v2) {
// Current and previous columns of the matrix
double[] curr = new double[v2.getDimensionality()];
double[] prev = new double[v2.getDimensionality()];
// size of edit distance band
// bandsize is the maximum allowed distance to the diagonal
int band = (int) Math.ceil(v2.getDimensionality() * bandSize);
// g parameter for local usage
double gValue = g;
for(int i = 0; i < v1.getDimensionality(); i++) {
// Swap current and prev arrays. We'll just overwrite the new curr.
{
double[] temp = prev;
prev = curr;
curr = temp;
}
int l = i - (band + 1);
if(l < 0) {
l = 0;
}
int r = i + (band + 1);
if(r > (v2.getDimensionality() - 1)) {
r = (v2.getDimensionality() - 1);
}
for(int j = l; j <= r; j++) {
if(Math.abs(i - j) <= band) {
// compute squared distance of feature vectors
double val1 = v1.doubleValue(i + 1);
double val2 = gValue;
double diff = (val1 - val2);
final double d1 = Math.sqrt(diff * diff);
val1 = gValue;
val2 = v2.doubleValue(j + 1);
diff = (val1 - val2);
final double d2 = Math.sqrt(diff * diff);
val1 = v1.doubleValue(i + 1);
val2 = v2.doubleValue(j + 1);
diff = (val1 - val2);
final double d12 = Math.sqrt(diff * diff);
final double dist1 = d1 * d1;
final double dist2 = d2 * d2;
final double dist12 = d12 * d12;
final double cost;
if((i + j) != 0) {
if((i == 0) || ((j != 0) && (((prev[j - 1] + dist12) > (curr[j - 1] + dist2)) && ((curr[j - 1] + dist2) < (prev[j] + dist1))))) {
// del
cost = curr[j - 1] + dist2;
}
else if((j == 0) || ((i != 0) && (((prev[j - 1] + dist12) > (prev[j] + dist1)) && ((prev[j] + dist1) < (curr[j - 1] + dist2))))) {
// ins
cost = prev[j] + dist1;
}
else {
// match
cost = prev[j - 1] + dist12;
}
}
else {
cost = 0;
}
curr[j] = cost;
// steps[i][j] = step;
}
else {
curr[j] = Double.POSITIVE_INFINITY; // outside band
}
}
}
return Math.sqrt(curr[v2.getDimensionality() - 1]);
}
@Override
public boolean equals(Object obj) {
if(!super.equals(obj)) {
return false;
}
return this.g == ((ERPDistanceFunction) obj).g;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractEditDistanceFunction.Parameterizer {
protected double g = 0.0;
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
final DoubleParameter gP = new DoubleParameter(G_ID, new GreaterEqualConstraint(0), 0.0);
if(config.grab(gP)) {
g = gP.getValue();
}
}
@Override
protected ERPDistanceFunction makeInstance() {
return new ERPDistanceFunction(bandSize, g);
}
}
}
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