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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) 2015
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.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.database.ids.DBIDs;
import de.lmu.ifi.dbs.elki.database.relation.Relation;
import de.lmu.ifi.dbs.elki.database.relation.RelationUtil;
import de.lmu.ifi.dbs.elki.utilities.BitsUtil;
/**
* Centroid only using a subset of dimensions.
*
* This class abstracts the mathematics of efficient and numerically stable
* computation of projected centroids.
*
* See {@link de.lmu.ifi.dbs.elki.utilities.DatabaseUtil DatabaseUtil} for
* easier to use APIs.
*
* @author Erich Schubert
* @since 0.4.0
*/
public class ProjectedCentroid extends Centroid {
/**
* The selected dimensions.
*/
private long[] dims;
/**
* Constructor for updating use.
*
* @param dims Dimensions to use (indexed with 0)
* @param dim Full dimensionality
*/
public ProjectedCentroid(long[] dims, int dim) {
super(dim);
this.dims = dims;
}
/**
* Add a single value with weight 1.0.
*
* @param val Value
*/
@Override
public void put(double[] val) {
assert (val.length == elements.length);
wsum += 1.0;
for(int i = BitsUtil.nextSetBit(dims, 0); i >= 0; i = BitsUtil.nextSetBit(dims, i + 1)) {
final double delta = val[i] - elements[i];
elements[i] += delta / wsum;
}
}
/**
* Add data with a given weight.
*
* @param val data
* @param weight weight
*/
@Override
public void put(double[] val, double weight) {
assert (val.length == elements.length);
if(weight == 0) {
return; // Skip zero weights.
}
final double nwsum = weight + wsum;
for(int i = BitsUtil.nextSetBit(dims, 0); i >= 0; i = BitsUtil.nextSetBit(dims, i + 1)) {
final double delta = val[i] - elements[i];
final double rval = delta * weight / nwsum;
elements[i] += rval;
}
wsum = nwsum;
}
/**
* Add a single value with weight 1.0.
*
* @param val Value
*/
@Override
public void put(NumberVector val) {
assert (val.getDimensionality() == elements.length);
wsum += 1.0;
for(int i = BitsUtil.nextSetBit(dims, 0); i >= 0; i = BitsUtil.nextSetBit(dims, i + 1)) {
final double delta = val.doubleValue(i) - elements[i];
elements[i] += delta / wsum;
}
}
/**
* Add data with a given weight.
*
* @param val data
* @param weight weight
*/
@Override
public void put(NumberVector val, double weight) {
assert (val.getDimensionality() == elements.length);
if(weight == 0) {
return; // Skip zero weights.
}
final double nwsum = weight + wsum;
for(int i = BitsUtil.nextSetBit(dims, 0); i >= 0; i = BitsUtil.nextSetBit(dims, i + 1)) {
final double delta = val.doubleValue(i) - elements[i];
final double rval = delta * weight / nwsum;
elements[i] += rval;
}
wsum = nwsum;
}
/**
* Static Constructor from a relation.
*
* @param dims Dimensions to use (indexed with 0)
* @param relation Relation to process
* @return Centroid
*/
public static ProjectedCentroid make(long[] dims, Relation<? extends NumberVector> relation) {
ProjectedCentroid c = new ProjectedCentroid(dims, RelationUtil.dimensionality(relation));
for(DBIDIter iditer = relation.iterDBIDs(); iditer.valid(); iditer.advance()) {
c.put(relation.get(iditer));
}
return c;
}
/**
* Static Constructor from a relation.
*
* @param dims Dimensions to use (indexed with 0)
* @param relation Relation to process
* @param ids IDs to process
* @return Centroid
*/
public static ProjectedCentroid make(long[] dims, Relation<? extends NumberVector> relation, DBIDs ids) {
ProjectedCentroid c = new ProjectedCentroid(dims, RelationUtil.dimensionality(relation));
for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
c.put(relation.get(iter));
}
return c;
}
}
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