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.math4.legacy.ml.distance; 018 019import org.apache.commons.math4.core.jdkmath.JdkMath; 020import org.apache.commons.math4.legacy.core.MathArrays; 021 022/** 023 * Calculates the Canberra distance between two points. 024 * 025 * @since 3.2 026 */ 027public class CanberraDistance implements DistanceMeasure { 028 /** {@inheritDoc} */ 029 @Override 030 public double compute(double[] a, double[] b) { 031 MathArrays.checkEqualLength(a, b); 032 double sum = 0; 033 for (int i = 0; i < a.length; i++) { 034 final double num = JdkMath.abs(a[i] - b[i]); 035 final double denom = JdkMath.abs(a[i]) + JdkMath.abs(b[i]); 036 sum += num == 0.0 && denom == 0.0 ? 0.0 : num / denom; 037 } 038 return sum; 039 } 040}