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The Hipparchus clustering module
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* This is not the original file distributed by the Apache Software Foundation
* It has been modified by the Hipparchus project
*/
package org.hipparchus.clustering.distance;
import org.hipparchus.exception.MathIllegalArgumentException;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathArrays;
/**
* Calculates the Canberra distance between two points.
*
*/
public class CanberraDistance implements DistanceMeasure {
/** Serializable version identifier. */
private static final long serialVersionUID = -6972277381587032228L;
/** {@inheritDoc} */
@Override
public double compute(double[] a, double[] b)
throws MathIllegalArgumentException {
MathArrays.checkEqualLength(a, b);
double sum = 0;
for (int i = 0; i < a.length; i++) {
final double num = FastMath.abs(a[i] - b[i]);
final double denom = FastMath.abs(a[i]) + FastMath.abs(b[i]);
sum += num == 0.0 && denom == 0.0 ? 0.0 : num / denom;
}
return sum;
}
}