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## Copyright (C) 1995-2013 Andreas Weingessel
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## Octave 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
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {} hamming (@var{m})
## Return the filter coefficients of a Hamming window of length @var{m}.
##
## For a definition of the Hamming window, see e.g., A. V. Oppenheim &
## R. W. Schafer, @cite{Discrete-Time Signal Processing}.
## @end deftypefn
## Author: AW <Andreas.Weingessel@ci.tuwien.ac.at>
## Description: Coefficients of the Hamming window
function c = hamming (m)
if (nargin != 1)
print_usage ();
endif
if (! (isscalar (m) && (m == fix (m)) && (m > 0)))
error ("hamming: M has to be an integer > 0");
endif
if (m == 1)
c = 1;
else
m = m - 1;
c = 0.54 - 0.46 * cos (2 * pi * (0:m)' / m);
endif
endfunction
%!assert (hamming (1), 1)
%!assert (hamming (2), (0.54 - 0.46)*ones (2,1))
%!assert (hamming (16), fliplr (hamming (16)))
%!assert (hamming (15), fliplr (hamming (15)))
%!test
%! N = 15;
%! A = hamming (N);
%! assert (A (ceil (N/2)), 1);
%!error hamming ()
%!error hamming (0.5)
%!error hamming (-1)
%!error hamming (ones (1,4))
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