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/*
 *  Copyright (c) 2007 - 2008 by Damien Di Fede 
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as published
 *   by the Free Software Foundation; either version 2 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 Library General Public License for more details.
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

package ddf.minim.analysis;

// TODO: Auto-generated Javadoc
/**
 * A Gauss window function.
 * 
 * @author Damien Di Fede
 * @author Corban Brook
 * @see The
 *      Gauss Window
 */
public class GaussWindow extends WindowFunction {
  
  /** The alpha. */
  double alpha;

  /**
   *  Constructs a Gauss window function.
   *
   * @param alpha the alpha
   */
  public GaussWindow(double alpha) {
    if (alpha < 0.0 || alpha > 0.5) {
      throw new RuntimeException("Range for GaussWindow out of bounds. Value must be <= 0.5");
    }
    this.alpha = alpha;
  }

  /** Constructs a Gauss window with a default alpha value of 0.25 */
  public GaussWindow() {
    this(0.25);
  }

  /* (non-Javadoc)
   * @see ddf.minim.analysis.WindowFunction#value(int, int)
   */
  protected double value(int length, int index) {
    return (double) Math.pow(Math.E,
        -0.5 * Math.pow((index - (length - 1) / (double) 2) / (this.alpha * (length - 1) / (double) 2), (double) 2));
  }
}