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## Copyright (C) 1996, 2000, 2003, 2004, 2005, 2006, 2007
## Auburn University. All rights reserved.
##
##
## 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; see the file COPYING. If not, see
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {[@var{c}, @var{tsam}, @var{input}, @var{output}] =} sys2fir (@var{sys})
##
## Extract @acronym{FIR} data from system data structure; see @command{fir2sys} for
## parameter descriptions.
## @seealso{fir2sys}
## @end deftypefn
## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu>
## Created: July 1996
function [c, tsam, inname, outname] = sys2fir (sys)
if (nargin != 1)
print_usage ();
endif
## let sys2tf do most of the work
[num, den, tsam, inname, outname] = sys2tf (sys);
alph = den(1); # scale to get monic denominator
den /= alph;
num /= alph;
l = length (den);
m = length (num);
if (norm (den(2:l)))
sysout (sys, "tf");
error ("denominator has poles away from origin");
elseif (! is_digital (sys))
error ("system must be discrete-time to be FIR");
elseif (m != l)
warning ("sys2fir: deg(num) - deg(den) = %d; coefficients must be shifted",
m-l);
endif
c = num;
endfunction
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