ddf.minim.analysis.BlackmanWindow Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of esp Show documentation

ESP - An EEG Signal Processing Library

There is a newer version: 2.1

/*
 *  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;

/**
 * A Blackman window function.
 * 
 * @author Damien Di Fede
 * @author Corban Brook
 * @see The
 *      Blackman Window
 */
public class BlackmanWindow extends WindowFunction {
  protected double alpha;

  /** Constructs a Blackman window. */
  public BlackmanWindow(double alpha) {
    this.alpha = alpha;
  }

  /** Constructs a Blackman window with a default alpha value of 0.16 */
  public BlackmanWindow() {
    this(0.16f);
  }

  protected double value(int length, int index) {
    double a0 = (1 - this.alpha) / 2f;
    double a1 = 0.5f;
    double a2 = this.alpha / 2f;

    return a0 - a1 * (double) Math.cos(TWO_PI * index / (length - 1)) + a2
        * (double) Math.cos(4 * Math.PI * index / (length - 1));
  }
}