1 files changed, 140 insertions, 0 deletions
diff --git a/elki/src/main/java/de/lmu/ifi/dbs/elki/utilities/referencepoints/RandomSampleReferencePoints.java b/elki/src/main/java/de/lmu/ifi/dbs/elki/utilities/referencepoints/RandomSampleReferencePoints.java
new file mode 100644
index 00000000..a8b17234
--- /dev/null
+++ b/elki/src/main/java/de/lmu/ifi/dbs/elki/utilities/referencepoints/RandomSampleReferencePoints.java
@@ -0,0 +1,140 @@
+package de.lmu.ifi.dbs.elki.utilities.referencepoints;
+
+/*
+ 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 java.util.ArrayList;
+import java.util.Collection;
+
+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.DBIDUtil;
+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.logging.LoggingUtil;
+import de.lmu.ifi.dbs.elki.math.random.RandomFactory;
+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.CommonConstraints;
+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.RandomParameter;
+
+/**
+ * Random-Sampling strategy for picking reference points.
+ * 
+ * @author Erich Schubert
+ */
+public class RandomSampleReferencePoints implements ReferencePointsHeuristic {
+  /**
+   * Sample size.
+   */
+  protected int samplesize;
+
+  /**
+   * Random generator.
+   */
+  protected RandomFactory rnd;
+
+  /**
+   * Constructor.
+   * 
+   * @param samplesize Sampling size
+   */
+  public RandomSampleReferencePoints(int samplesize, RandomFactory rnd) {
+    super();
+    this.samplesize = samplesize;
+    this.rnd = rnd;
+  }
+
+  @Override
+  public Collection<? extends NumberVector> getReferencePoints(Relation<? extends NumberVector> db) {
+    if(samplesize >= db.size()) {
+      LoggingUtil.warning("Requested sample size is larger than database size!");
+      return new RelationUtil.CollectionFromRelation<>(db);
+    }
+
+    DBIDs sample = DBIDUtil.randomSample(db.getDBIDs(), samplesize, rnd);
+
+    ArrayList<NumberVector> result = new ArrayList<>(sample.size());
+    for(DBIDIter it = sample.iter(); it.valid(); it.advance()) {
+      result.add(db.get(it));
+    }
+    return result;
+  }
+
+  /**
+   * Parameterization class.
+   * 
+   * @author Erich Schubert
+   * 
+   * @apiviz.exclude
+   */
+  public static class Parameterizer extends AbstractParameterizer {
+    /**
+     * Parameter to specify the sample size.
+     * <p>
+     * Key: {@code -sample.n}
+     * </p>
+     */
+    public static final OptionID N_ID = new OptionID("sample.n", "The number of samples to draw.");
+
+    /**
+     * Parameter to specify the sample size.
+     * <p>
+     * Key: {@code -sample.random}
+     * </p>
+     */
+    public static final OptionID RANDOM_ID = new OptionID("sample.random", "Random generator seed.");
+
+    /**
+     * Sample size.
+     */
+    protected int samplesize;
+
+    /**
+     * Random generator.
+     */
+    protected RandomFactory rnd;
+
+    @Override
+    protected void makeOptions(Parameterization config) {
+      super.makeOptions(config);
+      IntParameter samplesizeP = new IntParameter(N_ID)//
+      .addConstraint(CommonConstraints.GREATER_EQUAL_ONE_INT);
+      if(config.grab(samplesizeP)) {
+        samplesize = samplesizeP.intValue();
+      }
+      RandomParameter randomP = new RandomParameter(RANDOM_ID);
+      if(config.grab(randomP)) {
+        rnd = randomP.getValue();
+      }
+    }
+
+    @Override
+    protected RandomSampleReferencePoints makeInstance() {
+      return new RandomSampleReferencePoints(samplesize, rnd);
+    }
+  }
+}
+\ No newline at end of file