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package de.lmu.ifi.dbs.elki.algorithm.clustering;
/*
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.database.datastore.IntegerDataStore;
import de.lmu.ifi.dbs.elki.database.ids.ArrayModifiableDBIDs;
import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;
import de.lmu.ifi.dbs.elki.database.ids.DBIDs;
/**
* Utility functionality for writing clustering algorithms.
*
* @author Erich Schubert
*/
public class ClusteringAlgorithmUtil {
/**
* Collect clusters from their [0;k-1] integer labels.
*
* @param ids Objects
* @param assignment Cluster assignment
* @param k Number of labels (must be labeled 0 to k-1)
* @return Partitions
*/
public static ArrayModifiableDBIDs[] partitionsFromIntegerLabels(DBIDs ids, IntegerDataStore assignment, int k) {
int[] sizes = new int[k];
for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
sizes[assignment.intValue(iter)] += 1;
}
ArrayModifiableDBIDs[] clusters = new ArrayModifiableDBIDs[k];
for(int i = 0; i < k; i++) {
clusters[i] = DBIDUtil.newArray(sizes[i]);
}
for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
clusters[assignment.intValue(iter)].add(iter);
}
return clusters;
}
}
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