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+## Copyright (C) 1996 Auburn University.  All rights reserved.
+##
+## This file is part of Octave.
+##
+## Octave 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 2, or (at your option) any
+## later version.
+##
+## Octave 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 Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
+
+## -*- texinfo -*-
+##@deftypefn {Function File} {[@var{zer}, @var{pol}, @var{k}, @var{tsam}, @var{inname}, @var{outname}] =} sys2zp (@var{sys})
+## Extract zero/pole/leading coefficient information from a system data
+## structure
+##
+## See @ref{zp2sys} for parameter descriptions.
+##
+## @strong{Example}
+## @example
+## octave:1> sys=ss2sys([1 -2; -1.1,-2.1],[0;1],[1 1]);
+## octave:2> [zer,pol,k] = sys2zp(sys)
+## zer = 3.0000
+## pol =
+##   -2.6953
+##    1.5953
+## k = 1
+## @end example
+## @end deftypefn
+
+## Author: John Ingram <ingraje@eng.auburn.edu>
+## Created: July 15, 1996
+
+function [zer, pol, k, tsam, inname, outname] = sys2zp (sys)
+
+  if(nargin != 1)
+    usage("[zer,pol,k,tsam,inname,outname] = sys2zp(sys)");
+  elseif( !is_struct(sys))
+    error("sysconnect: sys must be in system data structure form")
+  elseif (! is_siso(sys) )
+    [n, nz, m, p] = sysdimensions(sys);
+    error(["system is not SISO (",num2str(m)," inputs, ...
+        ", num2str(p)," outputs"]);
+  endif
+
+  ## update zero-pole form
+  sys = sysupdate(sys,"zp");
+
+  zer = sys.zer;
+  pol = sys.pol;
+  k = sys.k;
+  tsam    = sysgettsam(sys);
+  inname  = sysgetsignals(sys,"in");
+  outname = sysgetsignals(sys,"out");
+
+endfunction
+
+