/**
* 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.
*/
package org.apache.mahout.utils;
import org.apache.hadoop.mapred.JobConf;
import org.apache.mahout.matrix.CardinalityException;
import org.apache.mahout.matrix.Vector;
import org.apache.mahout.utils.parameters.Parameter;
import java.util.Collection;
import java.util.Collections;
/**
* This class implements a Euclidian distance metric by summing the square root
* of the squared differences between each coordinate
*/
public class EuclideanDistanceMeasure implements DistanceMeasure {
@Override
public void configure(JobConf job) {
// nothing to do
}
@Override
public Collection<Parameter<?>> getParameters() {
return Collections.emptyList();
}
@Override
public void createParameters(String prefix, JobConf jobConf) {
// nothing to do
}
public static double distance(double[] p1, double[] p2) {
double result = 0.0;
for (int i = 0; i < p1.length; i++) {
double delta = p2[i] - p1[i];
result += delta * delta;
}
return Math.sqrt(result);
}
@Override
public double distance(Vector v1, Vector v2) {
if (v1.cardinality() != v2.cardinality())
throw new CardinalityException();
double result = 0;
for (int i = 0; i < v1.cardinality(); i++) {
double delta = v2.getQuick(i) - v1.getQuick(i);
result += delta * delta;
}
return Math.sqrt(result);
}
}