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) 2011
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/>.
*/

import de.lmu.ifi.dbs.elki.utilities.InspectionUtilFrequentlyScanned;

/**
 * WeightFunction interface that allows the use of various distance-based weight
 * functions. In addition to the distance parameter, the maximum distance and
 * standard deviation are also given, to allow distance functions to be
 * normalized according to the maximum or standard deviation.
 * 
 * @author Erich Schubert
 */
public interface WeightFunction extends InspectionUtilFrequentlyScanned {
  /**
   * Evaluate weight function with given parameters.
   * 
   * Note that usually implementations will ignore either max or stddev.
   * 
   * @param distance distance of the query point
   * @param max maximum distance of all included points
   * @param stddev standard deviation (i.e. quadratic mean / RMS) of the
   *        included points
   * @return weight for the query point
   */
  double getWeight(double distance, double max, double stddev);
}