--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/system/zp.m	Tue Feb 17 02:34:33 2004 +0000
@@ -0,0 +1,151 @@
+## Copyright (C) 1996, 1998 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} {} zp (@var{zer}, @var{pol}, @var{k}, @var{tsam}, @var{inname}, @var{outname})
+## Create system data structure from zero-pole data.
+##
+## @strong{Inputs}
+## @table @var
+## @item   zer
+## vector of system zeros
+## @item   pol
+## vector of system poles
+## @item   k
+## scalar leading coefficient
+## @item   tsam
+## sampling period. default: 0 (continuous system)
+## @item   inname
+## @itemx  outname
+## input/output signal names (lists of strings)
+## @end table
+##
+## @strong{Outputs}
+## sys: system data structure
+##
+## @strong{Example}
+## @example
+## octave:1> sys=zp([1 -1],[-2 -2 0],1);
+## octave:2> sysout(sys)
+## Input(s)
+##         1: u_1
+## Output(s):
+##         1: y_1
+## zero-pole form:
+## 1 (s - 1) (s + 1)
+## -----------------
+## s (s + 2) (s + 2)
+## @end example
+## @end deftypefn
+
+## Modified by John Ingram  July 20, 1996
+
+function outsys = zp (zer, pol, k, tsam, inname, outname)
+
+  ## Test for the correct number of input arguments
+  if ((nargin < 3) || (nargin > 6))
+    usage("outsys = zp(zer,pol,k[,tsam,inname,outname])");
+  endif
+
+  ## check input format
+  if( ! (isvector(zer) | isempty(zer) ) )
+    error("zer must be a vector or empty");
+  endif
+  if(!isempty(zer))
+    zer = reshape(zer,1,length(zer));           # make it a row vector
+  endif
+
+  if( ! (isvector(pol) | isempty(pol)))
+    error("pol must be a vector");
+  endif
+  if(!isempty(pol))
+    pol = reshape(pol,1,length(pol));
+  endif
+
+  if (! isscalar(k))
+     error("k must be a scalar");
+  endif
+
+  ## Test proper numbers of poles and zeros.  The number of poles must be
+  ## greater than or equal to the number of zeros.
+  if (length(zer) >  length(pol))
+    error(["number of poles (", num2str(length(pol)), ...
+        ") < number of zeros (", num2str(length(zer)),")"]);
+  endif
+
+  ## Set the system transfer function
+  outsys.zer = zer;
+  outsys.pol = pol;
+  outsys.k = k;
+
+  ## Set the system vector:  active = 1, updated = [0 1 0];
+  outsys.sys = [1, 0, 1, 0];
+
+  ## Set defaults
+  outsys.tsam = 0;
+  outsys.n = length(pol);
+  outsys.nz = 0;
+  outsys.yd = 0;        # assume (for now) continuous time outputs
+
+  ## Set the type of system
+  if (nargin > 3)
+    if( !isscalar(tsam) )
+      error("tsam must be a nonnegative scalar");
+    endif
+    if (tsam < 0)
+      error("sampling time must be positve")
+    elseif (tsam > 0)
+      [outsys.n,outsys.nz] = swap(outsys.n, outsys.nz);
+      outsys.yd = 1;            # discrete-time output
+    endif
+
+    outsys.tsam = tsam;
+  endif
+
+  outsys.inname = __sysdefioname__ (1, "u");
+  outsys.outname = __sysdefioname__ (1, "y");
+  outsys.stname = __sysdefstname__ (outsys.n, outsys.nz);
+
+  ## Set name of input
+  if (nargin > 4)
+    ## make sure its a string
+    if(!isempty(inname))
+      if(!iscell(inname))
+        inname = {inname}; 
+      endif
+      if(!is_signal_list(inname))
+        error("inname must be a single signal name");
+      endif
+      outsys.inname = inname(1);
+    endif
+  endif
+
+  ## Set name of output
+  if (nargin > 5)
+    if(!isempty(outname))
+      if(!iscell(outname))
+        outname = {outname};
+      endif
+      if(!is_signal_list(outname))
+        error("outname must be a single signal name");
+      endif
+      outsys.outname = outname(1);
+    endif
+  endif
+
+endfunction