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diff --git a/test/de/lmu/ifi/dbs/elki/utilities/datastructures/histogram/TestFlexiHistogram.java b/test/de/lmu/ifi/dbs/elki/utilities/datastructures/histogram/TestFlexiHistogram.java
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+++ b/test/de/lmu/ifi/dbs/elki/utilities/datastructures/histogram/TestFlexiHistogram.java
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+package de.lmu.ifi.dbs.elki.utilities.datastructures.histogram;
+
+/*
+ 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 static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import java.util.Random;
+
+import org.junit.Test;
+
+import de.lmu.ifi.dbs.elki.JUnit4Test;
+
+/**
+ * JUnit test to test the {@link AbstractObjDynamicHistogram} class.
+ * 
+ * @author Erich Schubert
+ */
+public class TestFlexiHistogram implements JUnit4Test {
+  /**
+   * Test that adds some data to the histogram and compares results.
+   */
+  @Test
+  public final void testObjHistogram() {
+    Double[] filled = { 0.0, 1.23, 4.56, 7.89, 0.0, null, null, null, null, null };
+    Double[] changed = { 0.0, 1.35, 8.01, 14.67, 9.01, 2.34, null, null, null, null };
+    Double[] resized = { -1.23, 1.35, 22.68, 11.35, 0.0, 0.0, -4.56, null, null, null };
+    Double[] expanded = { 1., 0.0, 0.0, 0.0, 0.0, 0.0, 29.59, null, null, null };
+    AbstractObjDynamicHistogram<Double> hist = new AbstractObjDynamicHistogram<Double>(5) {
+      @Override
+      public Double aggregate(Double first, Double second) {
+        return Double.valueOf(first.doubleValue() + second.doubleValue());
+      }
+
+      @Override
+      protected Double downsample(Object[] data, int start, int end, int size) {
+        double sum = 0;
+        for (int i = start; i < end; i++) {
+          final Double val = (Double) data[i];
+          if (val != null) {
+            sum += val;
+          }
+        }
+        return Double.valueOf(sum);
+      }
+
+      @Override
+      protected Double makeObject() {
+        return Double.valueOf(0.);
+      }
+
+      @Override
+      protected Double cloneForCache(Double data) {
+        return data;
+      }
+    };
+    hist.putData(0.0, 0.0);
+    hist.putData(0.15, 1.23);
+    hist.putData(0.25, 4.56);
+    hist.putData(0.35, 7.89);
+    hist.putData(0.5, 0.0);
+    hist.materialize();
+    assertArrayEquals("Filled histogram doesn't match", filled, hist.data);
+    hist.putData(0.15, 0.12);
+    hist.putData(0.25, 3.45);
+    hist.putData(0.35, 6.78);
+    hist.putData(0.45, 9.01);
+    hist.putData(0.55, 2.34);
+    assertArrayEquals("Changed histogram doesn't match", changed, hist.data);
+    hist.putData(-.13, -1.23);
+    hist.putData(1.13, -4.56);
+    assertArrayEquals("Resized histogram doesn't match", resized, hist.data);
+
+    // compare results via Iterator.
+    int off = 0;
+    for (ObjHistogram.Iter<Double> iter = hist.iter(); iter.valid(); iter.advance()) {
+      assertEquals("Array iterator bin position", -0.1 + 0.2 * off, iter.getCenter(), 0.00001);
+      assertEquals("Array iterator bin contents", resized[off], iter.getValue(), 0.00001);
+      off++;
+    }
+
+    // totally break out of the data range
+    hist.putData(-10., 1.);
+    assertArrayEquals("Expanded histogram doesn't match", expanded, hist.data);
+
+    // Try some random operations, too
+    Random r = new Random(0);
+    for (int i = 0; i < 1000; i++) {
+      hist.putData((r.nextDouble() - .5) * i * i, i * .1);
+    }
+  }
+
+  /**
+   * Test that adds some data to the histogram and compares results.
+   */
+  @Test
+  public final void testDoubleHistogram() {
+    double[] filled = { 0.0, 1.23, 4.56, 7.89, 0.0, 0, 0, 0, 0, 0 };
+    double[] changed = { 0.0, 1.35, 8.01, 14.67, 9.01, 2.34, 0, 0, 0, 0 };
+    double[] resized = { -1.23, 1.35, 22.68, 11.35, 0.0, 0.0, -4.56, 0, 0, 0 };
+    double[] expanded = { 1., 0.0, 0.0, 0.0, 0.0, 0.0, 29.59, 0, 0, 0 };
+    DoubleDynamicHistogram hist = new DoubleDynamicHistogram(5);
+    hist.increment(0.0, 0.0);
+    hist.increment(0.15, 1.23);
+    hist.increment(0.25, 4.56);
+    hist.increment(0.35, 7.89);
+    hist.increment(0.5, 0.0);
+    hist.materialize();
+    assertArrayEquals("Filled histogram doesn't match", filled, hist.data, 1E-15);
+    hist.increment(0.15, 0.12);
+    hist.increment(0.25, 3.45);
+    hist.increment(0.35, 6.78);
+    hist.increment(0.45, 9.01);
+    hist.increment(0.55, 2.34);
+    assertArrayEquals("Changed histogram doesn't match", changed, hist.data, 1E-15);
+    hist.increment(-.13, -1.23);
+    hist.increment(1.13, -4.56);
+    assertArrayEquals("Resized histogram doesn't match", resized, hist.data, 1E-15);
+
+    // compare results via Iterator.
+    int off = 0;
+    for (DoubleHistogram.Iter iter = hist.iter(); iter.valid(); iter.advance()) {
+      assertEquals("Array iterator bin position", -0.1 + 0.2 * off, iter.getCenter(), 0.00001);
+      assertEquals("Array iterator bin contents", resized[off], iter.getValue(), 0.00001);
+      off++;
+    }
+
+    // totally break out of the data range
+    hist.increment(-10., 1.);
+    assertArrayEquals("Expanded histogram doesn't match", expanded, hist.data, 1E-15);
+
+    // Try some random operations, too
+    Random r = new Random(0);
+    for (int i = 0; i < 1000; i++) {
+      hist.increment((r.nextDouble() - .5) * i * i, i * .1);
+    }
+  }
+}