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## Copyright (C) 1996, 1998, 2000, 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} {} fir2sys (@var{num}, @var{tsam}, @var{inname}, @var{outname})
## construct a system data structure from @acronym{FIR} description
##
## @strong{Inputs}
## @table @var
## @item num
## vector of coefficients
## @ifinfo
## [c0, c1, @dots{}, cn]
## @end ifinfo
## @iftex
## @tex
## $ [c_0, c_1, \ldots, c_n ]$
## @end tex
## @end iftex
## of the @acronym{SISO} @acronym{FIR} transfer function
## @ifinfo
## C(z) = c0 + c1*z^(-1) + c2*z^(-2) + @dots{} + cn*z^(-n)
## @end ifinfo
## @iftex
## @tex
## $$ C(z) = c_0 + c_1z^{-1} + c_2z^{-2} + \ldots + c_nz^{-n} $$
## @end tex
## @end iftex
##
## @item tsam
## sampling time (default: 1)
##
## @item inname
## name of input signal; may be a string or a list with a single entry.
##
## @item outname
## name of output signal; may be a string or a list with a single entry.
## @end table
##
## @strong{Output}
## @table @var
## @item sys
## system data structure
## @end table
##
## @strong{Example}
## @example
## octave:1> sys = fir2sys([1 -1 2 4],0.342,\
## > "A/D input","filter output");
## octave:2> sysout(sys)
## Input(s)
## 1: A/D input
##
## Output(s):
## 1: filter output (discrete)
##
## Sampling interval: 0.342
## transfer function form:
## 1*z^3 - 1*z^2 + 2*z^1 + 4
## -------------------------
## 1*z^3 + 0*z^2 + 0*z^1 + 0
## @end example
## @end deftypefn
## Author: R. Bruce Tenison <btenison@eng.auburn.edu>
## Created: July 29, 1994
## Name changed to TF2SYS July 1995
## updated for new system data structure format July 1996
## adapted from tf2sys july 1996
function sys = fir2sys (num, tsam, inname, outname)
## Test for the correct number of input arguments
if (nargin < 1 || nargin > 4)
print_usage ();
endif
## let tf do the argument checking
den = [1, zeros(1,length(num)-1)];
## check sampling interval (if any)
if (nargin < 2 || isempty (tsam))
tsam = 1; # default
endif
## Set name of input
if (nargin < 3)
inname = __sysdefioname__ (1, "u");
endif
## Set name of output
if (nargin < 4)
outname = __sysdefioname__ (1, "y");
endif
sys = tf (num, den, tsam, inname, outname);
endfunction
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