svn commit: r688704 - in /lucene/mahout/trunk/core/src: main/java/org/apache/mahout/utils/TanimotoDistanceMeasure.java test/java/org/apache/mahout/utils/TestTanimotoDistanceMeasure.java

[ka...@apache.org]

Author: kalle
Date: Mon Aug 25 05:29:35 2008
New Revision: 688704

URL: http://svn.apache.org/viewvc?rev=688704&view=rev
Log:
MAHOUT-42 : Tanimoto coefficient distance measure implementation

Added:
    lucene/mahout/trunk/core/src/main/java/org/apache/mahout/utils/TanimotoDistanceMeasure.java
    lucene/mahout/trunk/core/src/test/java/org/apache/mahout/utils/TestTanimotoDistanceMeasure.java

Added: lucene/mahout/trunk/core/src/main/java/org/apache/mahout/utils/TanimotoDistanceMeasure.java
URL: http://svn.apache.org/viewvc/lucene/mahout/trunk/core/src/main/java/org/apache/mahout/utils/TanimotoDistanceMeasure.java?rev=688704&view=auto
==============================================================================
--- lucene/mahout/trunk/core/src/main/java/org/apache/mahout/utils/TanimotoDistanceMeasure.java (added)
+++ lucene/mahout/trunk/core/src/main/java/org/apache/mahout/utils/TanimotoDistanceMeasure.java Mon Aug 25 05:29:35 2008
@@ -0,0 +1,104 @@
+package org.apache.mahout.utils;
+
+/*
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+
+import org.apache.mahout.matrix.Vector;
+import org.apache.mahout.matrix.Matrix;
+import org.apache.mahout.utils.DistanceMeasure;
+import org.apache.mahout.utils.WeightedDistanceMeasure;
+import org.apache.hadoop.mapred.JobConf;
+
+import java.util.HashSet;
+import java.util.Set;
+
+
+/**
+ * Tanimoto coefficient implementation.
+ *
+ * http://en.wikipedia.org/wiki/Jaccard_index
+ *
+ */
+public class TanimotoDistanceMeasure extends WeightedDistanceMeasure {
+
+  public TanimotoDistanceMeasure() {
+  }
+
+  /**
+   * Calculates the distance between two vectors.
+   *
+   * ((a^2 + b^2 - ab) / ab) - 1;
+   *
+   * @param vector0
+   * @param vector1
+   * @return 0 for perfect match, > 0 for greater distance
+   */
+  public double distance(Vector vector0, Vector vector1) {
+
+    // this whole distance measurent thing
+    // should be evaluated using an intermediate vector and BinaryFunction or something?
+    
+    Set<Integer> featuresSeen = new HashSet<Integer>((int)((vector0.size() + vector1.size()) * 0.75));
+
+    double ab = 0;
+    double a2 = 0;
+    double b2 = 0;
+
+    Double a;
+    Double b;
+    Double weight;
+
+    for (Vector.Element feature : vector0) {
+      if (!featuresSeen.add(feature.index())) {
+
+        a = feature.get();
+
+        b = vector1.get(feature.index());
+        if (b == null) {
+          b = 0d;
+        }
+
+        weight = getWeights() == null ? 1d : getWeights().get(feature.index());
+
+        ab += a * b * weight;
+        a2 += a * a * weight;
+        b2 += b * b * weight;
+      }
+    }
+
+
+    for (Vector.Element feature : vector1) {
+      if (!featuresSeen.add(feature.index())) {
+
+        a = vector0.get(feature.index());
+        if (a == null) {
+          a = 0d;
+        }
+
+        b = feature.get();
+
+        weight = getWeights() == null ? 1d : getWeights().get(feature.index());
+
+        ab += a * b * weight;
+        a2 += a * a * weight;
+        b2 += b * b * weight;
+      }
+    }
+
+    return (float)((a2 + b2 - ab) / ab) - 1;
+  }
+
+}
+

Added: lucene/mahout/trunk/core/src/test/java/org/apache/mahout/utils/TestTanimotoDistanceMeasure.java
URL: http://svn.apache.org/viewvc/lucene/mahout/trunk/core/src/test/java/org/apache/mahout/utils/TestTanimotoDistanceMeasure.java?rev=688704&view=auto
==============================================================================
--- lucene/mahout/trunk/core/src/test/java/org/apache/mahout/utils/TestTanimotoDistanceMeasure.java (added)
+++ lucene/mahout/trunk/core/src/test/java/org/apache/mahout/utils/TestTanimotoDistanceMeasure.java Mon Aug 25 05:29:35 2008
@@ -0,0 +1,24 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.mahout.utils;
+
+public class TestTanimotoDistanceMeasure extends DefaultWeightedDistanceMeasureTest {
+  public TanimotoDistanceMeasure distanceMeasureFactory() {
+    return new TanimotoDistanceMeasure();
+  }
+}