## Copyright (C) 1995-2015 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} {} bartlett (@var{m})
## Return the filter coefficients of a Bartlett (triangular) window of length
## @var{m}.
##
## For a definition of the Bartlett window see, e.g.,
## @nospell{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 Bartlett (triangular) window

function c = bartlett (m)

  if (nargin != 1)
    print_usage ();
  endif

  if (! (isscalar (m) && (m == fix (m)) && (m > 0)))
    error ("bartlett: M must be a positive integer");
  endif

  if (m == 1)
    c = 1;
  else
    m -= 1;
    n = fix (m / 2);
    c = [2*(0:n)/m, 2-2*(n+1:m)/m]';
  endif

endfunction


%!assert (bartlett (1), 1)
%!assert (bartlett (2), zeros (2,1))
%!assert (bartlett (15), flip (bartlett (15)), 5*eps)
%!assert (bartlett (16), flip (bartlett (16)), 5*eps)
%!test
%! N = 9;
%! A = bartlett (N);
%! assert (A(ceil (N/2)), 1);

%!error bartlett ()
%!error bartlett (0.5)
%!error bartlett (-1)
%!error bartlett (ones (1,4))