--- /dev/null
+## Copyright (C) 2008 Muthiah Annamalai <muthiah.annamalai@uta.edu>
+##
+## This program 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.
+##
+## 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 General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn{Function File} {m = } fht ( d, n, dim )
+## @cindex linear algebra
+## The function fht calculates Fast Hartley Transform
+## where @var{d} is the real input vector (matrix), and @var{m}
+## is the real-transform vector. For matrices the hartley transform
+## is calculated along the columns by default. The options
+## @var{n},and @var{dim} are similar to the options of FFT function.
+##
+## The forward and inverse hartley transforms are the same (except for a
+## scale factor of 1/N for the inverse hartley transform), but
+## implemented using different functions .
+##
+## The definition of the forward hartley transform for vector d,
+## @math{
+## m[K] = \sum_{i=0}^{N-1} d[i]*(cos[K*2*pi*i/N] + sin[K*2*pi*i/N]), for 0 <= K < N.
+## m[K] = \sum_{i=0}^{N-1} d[i]*CAS[K*i], for 0 <= K < N. }
+##
+## @example
+## fht(1:4)
+## @end example
+## @seealso{ifht,fft}
+## @end deftypefn
+
+function m = fht( d, n, dim )
+
+ if ( nargin < 1 )
+ print_usage();
+ end
+
+ if ( nargin == 3 )
+ Y = fft(d,n,dim);
+ elseif ( nargin == 2 )
+ Y = fft(d,n);
+ else
+ Y = fft(d);
+ end
+
+ m = real(Y) - imag(Y);
+
+# -- Traditional --
+# N = length(d);
+# for K = 1:N
+# i = 0:N-1;
+# t = 2*pi*(K-1).*i/N;
+# ker = (cos(t) + sin(t));
+# val = dot(d,ker);
+# m(K) = val;
+# end
+
+end
+%!
+%!assert( fht([1 2 3 4]),[10 -4 -2 0] )
+%!