CanberraDistance.java

  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. import org.apache.commons.math4.core.jdkmath.JdkMath;
  19. import org.apache.commons.math4.legacy.core.MathArrays;

  20. /**
  21.  * Calculates the Canberra distance between two points.
  22.  *
  23.  * @since 3.2
  24.  */
  25. public class CanberraDistance implements DistanceMeasure {
  26.     /** {@inheritDoc} */
  27.     @Override
  28.     public double compute(double[] a, double[] b) {
  29.         MathArrays.checkEqualLength(a, b);
  30.         double sum = 0;
  31.         for (int i = 0; i < a.length; i++) {
  32.             final double num = JdkMath.abs(a[i] - b[i]);
  33.             final double denom = JdkMath.abs(a[i]) + JdkMath.abs(b[i]);
  34.             sum += num == 0.0 && denom == 0.0 ? 0.0 : num / denom;
  35.         }
  36.         return sum;
  37.     }
  38. }