1 files changed, 139 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/datasource/filter/RandomSamplingStreamFilter.java b/src/de/lmu/ifi/dbs/elki/datasource/filter/RandomSamplingStreamFilter.java
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+++ b/src/de/lmu/ifi/dbs/elki/datasource/filter/RandomSamplingStreamFilter.java
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+package de.lmu.ifi.dbs.elki.datasource.filter;
+
+/*
+ This file is part of ELKI:
+ Environment for Developing KDD-Applications Supported by Index-Structures
+
+ Copyright (C) 2012
+ 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.Random;
+
+import de.lmu.ifi.dbs.elki.datasource.bundle.BundleMeta;
+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.IntervalConstraint;
+import de.lmu.ifi.dbs.elki.utilities.optionhandling.constraints.IntervalConstraint.IntervalBoundary;
+import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameterization.Parameterization;
+import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.DoubleParameter;
+import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.LongParameter;
+
+/**
+ * Subsampling stream filter.
+ * 
+ * @author Erich Schubert
+ */
+public class RandomSamplingStreamFilter extends AbstractStreamFilter {
+  /**
+   * Probability
+   */
+  protected double prob;
+
+  /**
+   * Random generator
+   */
+  protected Random random;
+
+  /**
+   * Constructor.
+   * 
+   * @param prob Probability
+   * @param seed Random seed
+   */
+  public RandomSamplingStreamFilter(double prob, Long seed) {
+    super();
+    this.prob = prob;
+    this.random = (seed != null) ? new Random(seed) : new Random();
+  }
+
+  @Override
+  public BundleMeta getMeta() {
+    return source.getMeta();
+  }
+
+  @Override
+  public Object data(int rnum) {
+    return source.data(rnum);
+  }
+
+  @Override
+  public Event nextEvent() {
+    while(true) {
+      Event ev = source.nextEvent();
+      switch(ev){
+      case END_OF_STREAM:
+        return ev;
+      case META_CHANGED:
+        return ev;
+      case NEXT_OBJECT:
+        if(random.nextDouble() < prob) {
+          return ev;
+        }
+        continue;
+      }
+    }
+  }
+
+  /**
+   * Parameterization class
+   * 
+   * @author Erich Schubert
+   * 
+   * @apiviz.exclude
+   */
+  public static class Parameterizer extends AbstractParameterizer {
+    /**
+     * Option ID for sampling probability
+     */
+    private static final OptionID PROB_ID = OptionID.getOrCreateOptionID("sampling.p", "Sampling probability. Each object has a chance of being samples with this probability.");
+
+    /**
+     * Option ID for random seed
+     */
+    private static final OptionID SEED_ID = OptionID.getOrCreateOptionID("sampling.seed", "Random generator seed for sampling.");
+
+    /**
+     * Probability
+     */
+    protected double prob;
+
+    /**
+     * Random seed
+     */
+    protected Long seed = null;
+
+    @Override
+    protected void makeOptions(Parameterization config) {
+      super.makeOptions(config);
+      DoubleParameter probP = new DoubleParameter(PROB_ID, new IntervalConstraint(0, IntervalBoundary.CLOSE, 1.0, IntervalBoundary.CLOSE));
+      if(config.grab(probP)) {
+        prob = probP.getValue();
+      }
+      LongParameter seedP = new LongParameter(SEED_ID, true);
+      if(config.grab(seedP)) {
+        seed = seedP.getValue();
+      }
+    }
+
+    @Override
+    protected RandomSamplingStreamFilter makeInstance() {
+      return new RandomSamplingStreamFilter(prob, seed);
+    }
+  }
+}