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deconv.m    84 lines (71 with data), 2.5 kB

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## Copyright (C) 2002 David Bateman
##
## 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} {} deconv (@var{y}, @var{a})
## Deconvolve two Galois vectors.
##
## @code{[b, r] = deconv (y, a)} solves for @var{b} and @var{r} such that
## @code{y = conv (a, b) + r}.
##
## If @var{y} and @var{a} are polynomial coefficient vectors, @var{b} will
## contain the coefficients of the polynomial quotient and @var{r} will be
## a remainder polynomial of lowest order.
## @seealso{conv}
## @end deftypefn
function [b, r] = deconv (y, a)
if (nargin != 2)
print_usage ();
endif
if (!isgalois (y) && !isgalois (a))
error ("deconv: at least one argument must be a galois variable");
elseif (!isgalois (y))
y = gf (y, a.m, a.prim_poly);
elseif (!isgalois (a))
a = gf (a, y.m, y.prim_poly);
elseif (a.m != y.m && a.prim_poly != y.prim_poly)
error ("deconv: both vectors must be in the same galois field");
endif
if (min (size (a)) > 1 || min (size (y)) > 1)
error ("deconv: both arguments must be vectors");
endif
la = length (a);
ly = length (y);
lb = ly - la + 1;
## Ensure that both vectors are row vectors.
if (rows (a) > 1)
a = reshape (a, 1, la);
endif
if (rows (y) > 1)
y = reshape (y, 1, ly);
endif
if (ly > la)
b = filter (y, a, [1, (zeros (1, ly - la))]);
elseif (ly == la)
b = filter (y, a, 1);
else
b = gf (0, y.m, y.prim_poly);
endif
lc = la + length (b) - 1;
if (ly == lc)
r = y - conv (a, b);
else
## Can't concatenate galois variables like this yet
## r = [(zeros (1, lc - ly)), y] - conv (a, b);
r = gf ([(zeros (1, lc - ly)), y], y.m, y.prim_poly) - conv (a, b);
endif
endfunction
%%Test input validation
%!error deconv (gf (1, 2), gf (1, 3))
%!error deconv (gf (eye (3), 3), gf (eye (3), 3))