Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / dftmtx.m

diff --git a/octave_packages/signal-1.1.3/dftmtx.m b/octave_packages/signal-1.1.3/dftmtx.m
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+++ b/octave_packages/signal-1.1.3/dftmtx.m
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+## Copyright (C) 2003 David Bateman <adb014@gmail.com>
+##
+## 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} {@var{d} = } dftmtx (@var{n})
+##
+## If @var{n} is a scalar, produces a @var{n}-by-@var{n} matrix @var{d}
+## such that the Fourier transform of a column vector of length @var{n}
+## is given by @code{dftmtx(@var{n}) * x} and the inverse Fourier transform
+## is given by @code{inv(dftmtx(@var{n})) * x}. In general this is less
+## efficient than calling the @dfn{fft} and @dfn{ifft} directly.
+## @end deftypefn
+
+function d = dftmtx(n)
+
+  if (nargin != 1)
+    print_usage;
+  elseif (!isscalar(n))
+    error ("dftmtx: argument must be scalar");
+  endif
+
+  d = fft(eye(n));
+
+endfunction