1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.math4.legacy.ml.distance; 18 19 import org.apache.commons.math4.core.jdkmath.JdkMath; 20 import org.apache.commons.math4.legacy.core.MathArrays; 21 22 /** 23 * Calculates the Canberra distance between two points. 24 * 25 * @since 3.2 26 */ 27 public class CanberraDistance implements DistanceMeasure { 28 /** {@inheritDoc} */ 29 @Override 30 public double compute(double[] a, double[] b) { 31 MathArrays.checkEqualLength(a, b); 32 double sum = 0; 33 for (int i = 0; i < a.length; i++) { 34 final double num = JdkMath.abs(a[i] - b[i]); 35 final double denom = JdkMath.abs(a[i]) + JdkMath.abs(b[i]); 36 sum += num == 0.0 && denom == 0.0 ? 0.0 : num / denom; 37 } 38 return sum; 39 } 40 }