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## See the file COPYRIGHT.md in the top-level directory of this
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## -*- texinfo -*-
## @deftypefn {} {@var{c} =} 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

function c = bartlett (m)

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

  if (! (isscalar (m) && m > 0 && m == fix (m)))
    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 <Invalid call> bartlett ()
%!error bartlett (0.5)
%!error bartlett (-1)
%!error bartlett (ones (1,4))
