001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.math3.ml.distance;
018
019import org.apache.commons.math3.util.FastMath;
020
021/**
022 * Calculates the Canberra distance between two points.
023 *
024 * @version $Id: CanberraDistance.html 885258 2013-11-03 02:46:49Z tn $
025 * @since 3.2
026 */
027public class CanberraDistance implements DistanceMeasure {
028
029    /** Serializable version identifier. */
030    private static final long serialVersionUID = -6972277381587032228L;
031
032    /** {@inheritDoc} */
033    public double compute(double[] a, double[] b) {
034        double sum = 0;
035        for (int i = 0; i < a.length; i++) {
036            final double num = FastMath.abs(a[i] - b[i]);
037            final double denom = FastMath.abs(a[i]) + FastMath.abs(b[i]);
038            sum += num == 0.0 && denom == 0.0 ? 0.0 : num / denom;
039        }
040        return sum;
041    }
042
043}