1 files changed, 141 insertions, 0 deletions
diff --git a/elki/src/main/java/de/lmu/ifi/dbs/elki/evaluation/classification/holdout/RandomizedCrossValidation.java b/elki/src/main/java/de/lmu/ifi/dbs/elki/evaluation/classification/holdout/RandomizedCrossValidation.java
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--- /dev/null
+++ b/elki/src/main/java/de/lmu/ifi/dbs/elki/evaluation/classification/holdout/RandomizedCrossValidation.java
@@ -0,0 +1,141 @@
+package de.lmu.ifi.dbs.elki.evaluation.classification.holdout;
+
+/*
+ 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.Random;
+
+import de.lmu.ifi.dbs.elki.datasource.bundle.MultipleObjectsBundle;
+import de.lmu.ifi.dbs.elki.math.random.RandomFactory;
+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;
+
+/**
+ * RandomizedCrossValidationHoldout provides a set of partitions of a database
+ * to perform cross-validation. The test sets are not guaranteed to be disjoint.
+ * 
+ * @author Arthur Zimek
+ */
+public class RandomizedCrossValidation extends RandomizedHoldout {
+  /**
+   * Holds the number of folds, current fold.
+   */
+  protected int nfold, fold;
+
+  /**
+   * Constructor for n-fold cross-validation.
+   * 
+   * @param random Random seed
+   * @param nfold Number of folds
+   */
+  public RandomizedCrossValidation(RandomFactory random, int nfold) {
+    super(random);
+    this.nfold = nfold;
+  }
+
+  @Override
+  public void initialize(MultipleObjectsBundle bundle) {
+    super.initialize(bundle);
+    this.fold = 0;
+  }
+
+  @Override
+  public int numberOfPartitions() {
+    return nfold;
+  }
+
+  @Override
+  public TrainingAndTestSet nextPartitioning() {
+    if(fold >= nfold) {
+      return null;
+    }
+    MultipleObjectsBundle training = new MultipleObjectsBundle();
+    MultipleObjectsBundle test = new MultipleObjectsBundle();
+    Random rnd = random.getRandom();
+    int datalen = bundle.dataLength();
+
+    boolean[] assignment = new boolean[datalen];
+    int trsize = 0, tesize = 0;
+    for(int i = 0; i < assignment.length; ++i) {
+      boolean p = rnd.nextInt(nfold) < nfold - 1;
+      assignment[i] = p;
+      @SuppressWarnings("unused")
+      int discard = p ? ++trsize : ++tesize;
+    }
+    // Process column-wise.
+    for(int c = 0, cs = bundle.metaLength(); c < cs; ++c) {
+      ArrayList<Object> tr = new ArrayList<>(trsize), te = new ArrayList<>(tesize);
+      for(int i = 0; i < datalen; ++i) {
+        (assignment[i] ? tr : te).add(bundle.data(i, c));
+      }
+      training.appendColumn(bundle.meta(c), tr);
+      test.appendColumn(bundle.meta(c), te);
+    }
+
+    ++fold;
+    return new TrainingAndTestSet(training, test, labels);
+  }
+
+  /**
+   * Parameterization class
+   * 
+   * @author Erich Schubert
+   * 
+   * @apiviz.exclude
+   */
+  public static class Parameterizer extends RandomizedHoldout.Parameterizer {
+    /**
+     * Parameter for number of folds.
+     */
+    public static final OptionID NFOLD_ID = new OptionID("nfold", "positive number of folds for cross-validation");
+
+    /**
+     * Default number of folds.
+     */
+    public static final int N_DEFAULT = 10;
+
+    /**
+     * Holds the number of folds.
+     */
+    protected int nfold;
+
+    @Override
+    protected void makeOptions(Parameterization config) {
+      super.makeOptions(config);
+      IntParameter nfoldP = new IntParameter(NFOLD_ID)//
+      .setDefaultValue(N_DEFAULT) //
+      .addConstraint(CommonConstraints.GREATER_EQUAL_ONE_INT);
+      if(config.grab(nfoldP)) {
+        nfold = nfoldP.intValue();
+      }
+    }
+
+    @Override
+    protected RandomizedCrossValidation makeInstance() {
+      return new RandomizedCrossValidation(random, nfold);
+    }
+  }
+}
+\ No newline at end of file