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package de.lmu.ifi.dbs.elki.algorithm.outlier.spatial.neighborhood.weighted;
/*
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.Collection;
import java.util.List;
import de.lmu.ifi.dbs.elki.algorithm.outlier.spatial.neighborhood.NeighborSetPredicate;
import de.lmu.ifi.dbs.elki.data.type.TypeInformation;
import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.database.ids.DBIDRef;
import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;
import de.lmu.ifi.dbs.elki.database.ids.DBIDs;
import de.lmu.ifi.dbs.elki.database.ids.DoubleDBIDPair;
import de.lmu.ifi.dbs.elki.database.ids.ModifiableDBIDs;
import de.lmu.ifi.dbs.elki.database.relation.Relation;
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;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.ObjectParameter;
/**
* Neighborhood obtained by computing the k-fold closure of an existing
* neighborhood. Objects are weighted linearly by their distance: the object
* itself has a weight of 1 and this decreases linearly to 1/(n+1) for the
* nth-step neighbors.
*
* TODO: make actual weighting parameterizable?
*
* @author Erich Schubert
*/
public class LinearWeightedExtendedNeighborhood implements WeightedNeighborSetPredicate {
/**
* The data store to use
*/
private NeighborSetPredicate inner;
/**
* The number of steps to extend to.
*/
private int steps;
/**
* Constructor.
*
* @param inner Inner neighborhood
* @param steps Number of steps to expand
*/
public LinearWeightedExtendedNeighborhood(NeighborSetPredicate inner, int steps) {
super();
this.inner = inner;
this.steps = steps;
}
/**
* Compute the weight from the number of steps needed.
*
* @param tsteps steps to target
* @return weight
*/
private double computeWeight(int tsteps) {
return 1.0 - (tsteps / (float) (steps + 1));
}
@Override
public Collection<DoubleDBIDPair> getWeightedNeighbors(DBIDRef reference) {
ModifiableDBIDs seen = DBIDUtil.newHashSet();
List<DoubleDBIDPair> result = new ArrayList<>();
// Add starting object
result.add(DBIDUtil.newPair(computeWeight(0), reference));
seen.add(reference);
// Extend.
DBIDs cur = DBIDUtil.deref(reference);
for(int i = 1; i <= steps; i++) {
final double weight = computeWeight(i);
// Collect newly discovered IDs
ModifiableDBIDs add = DBIDUtil.newHashSet();
for(DBIDIter iter = cur.iter(); iter.valid(); iter.advance()) {
for(DBIDIter iter2 = inner.getNeighborDBIDs(iter).iter(); iter2.valid(); iter2.advance()) {
// Seen before?
if(seen.contains(iter2)) {
continue;
}
add.add(iter2);
result.add(DBIDUtil.newPair(weight, iter2));
}
}
if(add.size() == 0) {
break;
}
cur = add;
}
return result;
}
/**
* Factory class.
*
* @author Erich Schubert
*
* @apiviz.stereotype factory
* @apiviz.has LinearWeightedExtendedNeighborhood oneway - - «produces»
*/
public static class Factory<O> implements WeightedNeighborSetPredicate.Factory<O> {
/**
* Inner neighbor set predicate
*/
private NeighborSetPredicate.Factory<O> inner;
/**
* Number of steps to do
*/
private int steps;
/**
* Constructor.
*
* @param inner Inner neighbor set predicate
* @param steps Number of steps to do
*/
public Factory(NeighborSetPredicate.Factory<O> inner, int steps) {
super();
this.inner = inner;
this.steps = steps;
}
@Override
public LinearWeightedExtendedNeighborhood instantiate(Relation<? extends O> database) {
return new LinearWeightedExtendedNeighborhood(inner.instantiate(database), steps);
}
@Override
public TypeInformation getInputTypeRestriction() {
return inner.getInputTypeRestriction();
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer<O> extends AbstractParameterizer {
/**
* Parameter to specify the neighborhood predicate to use.
*/
public static final OptionID NEIGHBORHOOD_ID = new OptionID("extendedneighbors.neighborhood", "The inner neighborhood predicate to use.");
/**
* Parameter to specify the number of steps allowed
*/
public static final OptionID STEPS_ID = new OptionID("extendedneighbors.steps", "The number of steps allowed in the neighborhood graph.");
/**
* The number of steps to do.
*/
private int steps;
/**
* Inner neighbor set predicate
*/
private NeighborSetPredicate.Factory<O> inner;
/**
* Inner neighborhood parameter.
*
* @param config Parameterization
* @return Inner neighborhood.
*/
protected static <O> NeighborSetPredicate.Factory<O> getParameterInnerNeighborhood(Parameterization config) {
final ObjectParameter<NeighborSetPredicate.Factory<O>> param = new ObjectParameter<>(NEIGHBORHOOD_ID, NeighborSetPredicate.Factory.class);
if(config.grab(param)) {
return param.instantiateClass(config);
}
return null;
}
@Override
protected void makeOptions(Parameterization config) {
super.makeOptions(config);
inner = getParameterInnerNeighborhood(config);
steps = getParameterSteps(config);
}
/**
* Get the number of steps to do in the neighborhood graph.
*
* @param config Parameterization
* @return number of steps, default 1
*/
public static int getParameterSteps(Parameterization config) {
final IntParameter param = new IntParameter(STEPS_ID);
param.addConstraint(new GreaterEqualConstraint(1));
if(config.grab(param)) {
return param.getValue();
}
return 1;
}
@Override
protected LinearWeightedExtendedNeighborhood.Factory<O> makeInstance() {
return new LinearWeightedExtendedNeighborhood.Factory<>(inner, steps);
}
}
}
}
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