/*
* Source Code for Listing 10.6
*
*/
package mia.clustering.ch10;
import java.util.Collection;
import java.util.Collections;
import org.apache.hadoop.conf.Configuration;
import org.apache.mahout.common.distance.DistanceMeasure;
import org.apache.mahout.common.parameters.Parameter;
import org.apache.mahout.math.CardinalityException;
import org.apache.mahout.math.Vector;
public class MyDistanceMeasure implements DistanceMeasure {
@Override
public double distance(Vector v1, Vector v2) {
if (v1.size() != v2.size()) {
throw new CardinalityException(v1.size(), v2.size());
}
double lengthSquaredv1 = v1.getLengthSquared();
double lengthSquaredv2 = v2.getLengthSquared();
double dotProduct = v2.dot(v1);
double denominator = Math.sqrt(lengthSquaredv1)
* Math.sqrt(lengthSquaredv2);
// correct for floating-point rounding errors
if (denominator < dotProduct) {
denominator = dotProduct;
}
double distance = 1.0 - dotProduct / denominator;
if (distance < 0.5) {
return (1 - distance) * (distance * distance) + distance
* Math.sqrt(distance);
} else return Math.sqrt(distance);
}
@Override
public double distance(double centroidLengthSquare,
Vector centroid,
Vector v) {
return distance(centroid, v);
}
@Override
public Collection<Parameter<?>> getParameters() {
return Collections.emptyList();
}
@Override
public void createParameters(String prefix, Configuration jobConf) {
// TODO Auto-generated method stub
}
@Override
public void configure(Configuration config) {
// TODO Auto-generated method stub
}
}