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package de.lmu.ifi.dbs.elki.math.linearalgebra.pca.weightfunctions;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2015
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* Quadratic weight function, scaled using the maximum to reach 0.1 at that
* point.
*
* 1.0 - 0.9 * (distance/max)^2
*
* @author Erich Schubert
*/
public final class QuadraticWeight implements WeightFunction {
/**
* Evaluate quadratic weight. stddev is ignored.
*/
@Override
public double getWeight(double distance, double max, double stddev) {
if(max <= 0) {
return 1.0;
}
double relativedistance = distance / max;
return 1.0 - 0.9 * relativedistance * relativedistance;
}
}
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