R/blackman.R

In signal: Signal Processing

## Copyright (C) 1995, 1996, 1997  Andreas Weingessel
##
## This file is part of Octave.
##
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## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2, or (at your option)
## any later version.
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## General Public License for more details.
##
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## along with Octave; see the file COPYING.  If not, write to the Free
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## -*- texinfo -*-
## @deftypefn {Function File} {} blackman (@var{m})
## Return the filter coefficients of a Blackman window of length @var{m}.
##
## For a definition of the  Blackman window, see e.g. A. V. Oppenheim &
## R. W. Schafer, "Discrete-Time Signal Processing".
## @} # deftypefn

## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at>
## Description: Coefficients of the Blackman window

blackman  <- function(n)  {
  if (! (length(n) == 1 && (n == round(n)) && (n > 0)))
    stop("n has to be an integer > 0")
  if (n == 1)
    c <- 1
  else {
    n <- n - 1
    k <- (0 : n) / n
    c <- 0.42 - 0.5 * cos(2 * pi * k) + 0.08 * cos(4 * pi * k)
  }
  c
}