1 files changed, 174 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/datasource/filter/transform/NumberVectorRandomFeatureSelectionFilter.java b/src/de/lmu/ifi/dbs/elki/datasource/filter/transform/NumberVectorRandomFeatureSelectionFilter.java
new file mode 100644
index 00000000..7d799a1e
--- /dev/null
+++ b/src/de/lmu/ifi/dbs/elki/datasource/filter/transform/NumberVectorRandomFeatureSelectionFilter.java
@@ -0,0 +1,174 @@
+package de.lmu.ifi.dbs.elki.datasource.filter.transform;
+
+/*
+ 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.BitSet;
+
+import de.lmu.ifi.dbs.elki.data.DoubleVector;
+import de.lmu.ifi.dbs.elki.data.NumberVector;
+import de.lmu.ifi.dbs.elki.data.VectorUtil;
+import de.lmu.ifi.dbs.elki.data.type.SimpleTypeInformation;
+import de.lmu.ifi.dbs.elki.data.type.TypeUtil;
+import de.lmu.ifi.dbs.elki.data.type.VectorFieldTypeInformation;
+import de.lmu.ifi.dbs.elki.datasource.filter.AbstractVectorStreamConversionFilter;
+import de.lmu.ifi.dbs.elki.utilities.RandomFactory;
+import de.lmu.ifi.dbs.elki.utilities.Util;
+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.RandomParameter;
+
+/**
+ * Parser to project the ParsingResult obtained by a suitable base parser onto a
+ * randomly selected subset of attributes.
+ * 
+ * @author Arthur Zimek
+ * 
+ * @apiviz.uses NumberVector
+ * 
+ * @param <V> vector type
+ */
+public class NumberVectorRandomFeatureSelectionFilter<V extends NumberVector<?>> extends AbstractVectorStreamConversionFilter<V, V> {
+  /**
+   * The selected attributes.
+   */
+  protected BitSet selectedAttributes = null;
+
+  /**
+   * Holds the desired cardinality of the subset of attributes selected for
+   * projection.
+   */
+  protected int k;
+
+  /**
+   * Holds a random generator.
+   */
+  protected RandomFactory rnd;
+
+  /**
+   * Constructor.
+   * 
+   * @param dim Dimensionality
+   * @param rnd Random generator
+   */
+  public NumberVectorRandomFeatureSelectionFilter(int dim, RandomFactory rnd) {
+    super();
+    this.k = dim;
+    this.rnd = rnd;
+  }
+
+  @Override
+  protected V filterSingleObject(V obj) {
+    return VectorUtil.project(obj, selectedAttributes, factory);
+  }
+
+  @Override
+  protected SimpleTypeInformation<? super V> getInputTypeRestriction() {
+    return TypeUtil.NUMBER_VECTOR_FIELD;
+  }
+
+  @Override
+  protected SimpleTypeInformation<? super V> convertedType(SimpleTypeInformation<V> in) {
+    initializeRandomAttributes(in);
+    initializeOutputType(in);
+    return new VectorFieldTypeInformation<V>(factory, k);
+  }
+
+  /**
+   * Initialize random attributes.
+   * 
+   * Invoke this from {@link #convertedType}!
+   * 
+   * @param in Type information.
+   */
+  void initializeRandomAttributes(SimpleTypeInformation<V> in) {
+    int d = ((VectorFieldTypeInformation<V>) in).getDimensionality();
+    selectedAttributes = Util.randomBitSet(k, d, rnd.getRandom());
+  }
+
+  /**
+   * Parameterization class.
+   * 
+   * @author Erich Schubert
+   * 
+   * @apiviz.exclude
+   */
+  public static class Parameterizer extends AbstractParameterizer {
+    /**
+     * Parameter for the desired cardinality of the subset of attributes
+     * selected for projection.
+     * 
+     * <p>
+     * Key: <code>-randomprojection.numberselected</code>
+     * </p>
+     * <p>
+     * Default: <code>1</code>
+     * </p>
+     * <p>
+     * Constraint: &ge;1
+     * </p>
+     */
+    public static final OptionID NUMBER_SELECTED_ATTRIBUTES_ID = new OptionID("randomprojection.numberselected", "number of selected attributes");
+
+    /**
+     * Optional parameter to specify a seed for random projection. If unused,
+     * system time is used as seed.
+     * <p>
+     * Key: {@code -randomprojection.seed}
+     * </p>
+     */
+    public static final OptionID SEED_ID = new OptionID("randomprojection.seed", "Seed for random selection of projection attributes.");
+
+    /**
+     * Number of attributes to select.
+     */
+    protected int k = 0;
+
+    /**
+     * Random generator.
+     */
+    protected RandomFactory rnd;
+
+    @Override
+    protected void makeOptions(Parameterization config) {
+      super.makeOptions(config);
+      IntParameter kP = new IntParameter(NUMBER_SELECTED_ATTRIBUTES_ID, 1);
+      kP.addConstraint(new GreaterEqualConstraint(1));
+      if (config.grab(kP)) {
+        k = kP.getValue().intValue();
+      }
+      RandomParameter rndP = new RandomParameter(SEED_ID);
+      if (config.grab(rndP)) {
+        rnd = rndP.getValue();
+      }
+    }
+
+    @Override
+    protected NumberVectorRandomFeatureSelectionFilter<DoubleVector> makeInstance() {
+      return new NumberVectorRandomFeatureSelectionFilter<DoubleVector>(k, rnd);
+    }
+  }
+}