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 }