1 files changed, 46 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/ml/distance/CanberraDistance.java b/src/main/java/org/apache/commons/math3/ml/distance/CanberraDistance.java
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+/*
+ * 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
+ *
+ *      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.
+ */
+package org.apache.commons.math3.ml.distance;
+
+import org.apache.commons.math3.exception.DimensionMismatchException;
+import org.apache.commons.math3.util.FastMath;
+import org.apache.commons.math3.util.MathArrays;
+
+/**
+ * Calculates the Canberra distance between two points.
+ *
+ * @since 3.2
+ */
+public class CanberraDistance implements DistanceMeasure {
+
+    /** Serializable version identifier. */
+    private static final long serialVersionUID = -6972277381587032228L;
+
+    /** {@inheritDoc} */
+    public double compute(double[] a, double[] b)
+    throws DimensionMismatchException {
+        MathArrays.checkEqualLength(a, b);
+        double sum = 0;
+        for (int i = 0; i < a.length; i++) {
+            final double num = FastMath.abs(a[i] - b[i]);
+            final double denom = FastMath.abs(a[i]) + FastMath.abs(b[i]);
+            sum += num == 0.0 && denom == 0.0 ? 0.0 : num / denom;
+        }
+        return sum;
+    }
+
+}