# HG changeset patch
# User jwe
# Date 1076985273 0
# Node ID f105000ab25cdc8f3baa3e3c6725ae1c9ad18d3a
# Parent  567c8e2d2438b69cba86d0135a53fd6710206d08
[project @ 2004-02-17 02:34:33 by jwe]

diff -r 567c8e2d2438 -r f105000ab25c scripts/control/system/__sysconcat__.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/system/__sysconcat__.m	Tue Feb 17 02:34:33 2004 +0000
@@ -0,0 +1,23 @@
+function c = __sysconcat__(a,b)
+  # c = __sysconcat__(a,b)
+  # cell array replacement for append, used by control systems toolbox
+
+  if(isstr(a))
+    a = {a};
+  endif
+  if(isstr(b))
+    b = {b};
+  endif
+
+  if ( ! ( is_signal_list(a)  && is_signal_list(b) ) )
+    error("need cell arrays of strings");
+  endif
+
+  c = a;
+  la = length(a);
+  for ii=1:length(b)
+    c{la+ii} = b{ii};
+  endfor
+
+endfunction
+
diff -r 567c8e2d2438 -r f105000ab25c scripts/control/system/__tfl__.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/system/__tfl__.m	Tue Feb 17 02:34:33 2004 +0000
@@ -0,0 +1,35 @@
+## 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} {} __tfl__ (@var{vec})
+## used internally in tf.
+## strip leading zero coefficients to get the true polynomial length
+## @end deftypefn
+
+function vec = __tfl__ (vec)
+
+  while (length (vec) > 1 && vec(1) == 0)
+    vec = vec (2:end);
+  endwhile
+
+  if (vec(1) == 0)
+    warning ("tf: polynomial has no nonzero coefficients!")
+  endif
+
+endfunction
diff -r 567c8e2d2438 -r f105000ab25c scripts/control/system/cellidx.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/system/cellidx.m	Tue Feb 17 02:34:33 2004 +0000
@@ -0,0 +1,97 @@
+## Copyright (C) 2000 2004 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{idxvec}, @var{errmsg}] =} listidx (@var{listvar}, @var{strlist})
+## Return indices of string entries in @var{listvar} that match strings
+## in @var{strlist}.
+##
+## Both @var{listvar} and @var{strlist} may be passed as strings or
+## string matrices.  If they are passed as string matrices, each entry
+## is processed by @code{deblank} prior to searching for the entries.
+##
+## The first output is the vector of indices in @var{listvar}.
+##
+## If @var{strlist} contains a string not in @var{listvar}, then
+## an error message is returned in @var{errmsg}.  If only one output
+## argument is requested, then @var{listidx} prints @var{errmsg} to the
+## screen and exits with an error.
+## @end deftypefn
+
+function [idxvec,errmsg]  = cellidx(listvar,strlist)
+
+if(nargin != 2)
+  usage("idxvec = cellidx(listvar,strlist)");
+endif
+
+if(isstr(strlist))
+  tmp = strlist;
+  strlist = {};
+  for kk=1:rows(tmp)
+    strlist{kk} = deblank(tmp(kk,:));
+  endfor
+endif
+
+if(isstr(listvar))
+  tmp = listvar;
+  listvar = {};
+  for kk=1:rows(tmp)
+    listvar{kk} = deblank(tmp(kk,:));
+  endfor
+endif
+
+## initialize size of idxvec (for premature return)
+idxvec = zeros(length(strlist),1);
+
+errmsg = "";
+if(!is_signal_list(listvar))
+  errmsg = "listvar must be a list of strings";
+elseif(!is_signal_list(strlist))
+  errmsg = "strlist must be a list of strings";
+endif
+
+if(length(errmsg))
+  if(nargout < 2) error(errmsg);
+  else return;
+  endif
+endif
+
+nsigs = length(listvar);
+for idx = 1:length(strlist)
+  signame = strlist{idx};
+  for jdx = 1:nsigs
+    if( strcmp(signame,listvar{jdx}) )
+      if(idxvec(idx) != 0)
+        warning("Duplicate signal name %s (%d,%d)\n", ...
+          listvar{jdx},jdx,idxvec(idx));
+      else
+        idxvec(idx) = jdx;
+      endif
+    endif
+  endfor
+  if(idxvec(idx) == 0)
+    errmsg = sprintf("Did not find %s",signame);
+    if(nargout == 1)
+      error(errmsg);
+    else
+      break
+    end
+  endif
+endfor
+
+endfunction
diff -r 567c8e2d2438 -r f105000ab25c scripts/control/system/ss.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/system/ss.m	Tue Feb 17 02:34:33 2004 +0000
@@ -0,0 +1,287 @@
+## 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} {} ss (@var{a}, @var{b}, @var{c}, @var{d}, @var{tsam}, @var{n}, @var{nz}, @var{stname}, @var{inname}, @var{outname}, @var{outlist})
+## Create system structure from state-space data.   May be continous,
+## discrete, or mixed (sampeled-data)
+##
+## @strong{Inputs}
+## @table @var
+## @item a
+## @itemx b
+## @itemx c
+## @itemx d
+## usual state space matrices.
+##
+## default: @var{d} = zero matrix
+##
+## @item   tsam
+## sampling rate.  Default: @math{tsam = 0} (continuous system)
+##
+## @item n
+## @itemx nz
+## number of continuous, discrete states in the system
+##
+## If @var{tsam} is 0, @math{n = @code{rows}(@var{a})}, @math{nz = 0}.
+##
+## If @var{tsam} is greater than zero, @math{n = 0},
+## @math{nz = @code{rows}(@var{a})}
+##
+## see below for system partitioning
+##
+## @item  stname
+## list of strings of state signal names
+##
+## default (@var{stname}=[] on input): @code{x_n} for continuous states,
+##                     @code{xd_n} for discrete states
+##
+## @item inname
+## list of strings of input signal names
+##
+## default (@var{inname} = [] on input): @code{u_n}
+##
+## @item outname
+## list of strings of input signal names
+##
+## default (@var{outname} = [] on input): @code{y_n}
+##
+## @item   outlist
+##
+## list of indices of outputs y that are sampled
+##
+## If @var{tsam} is 0, @math{outlist = []}.
+##
+## If @var{tsam} is greater than 0, @math{outlist = 1:@code{rows}(@var{c})}.
+## @end table
+##
+## Unlike states, discrete/continous outputs may appear in any order.
+##
+## @strong{Note} @code{sys2ss} returns a vector @var{yd} where
+## @var{yd}(@var{outlist}) = 1; all other entries of @var{yd} are 0.
+##
+## @strong{Outputs}
+## @var{outsys} = system data structure
+##
+## @strong{System partitioning}
+##
+## Suppose for simplicity that outlist specified
+## that the first several outputs were continuous and the remaining outputs
+## were discrete.  Then the system is partitioned as
+## @example
+## @group
+## x = [ xc ]  (n x 1)
+##     [ xd ]  (nz x 1 discrete states)
+## a = [ acc acd ]  b = [ bc ]
+##     [ adc add ]      [ bd ]
+## c = [ ccc ccd ]  d = [ dc ]
+##     [ cdc cdd ]      [ dd ]
+##
+##     (cdc = c(outlist,1:n), etc.)
+## @end group
+## @end example
+## with dynamic equations:
+## @ifinfo
+## @math{d/dt xc(t)     = acc*xc(t)      + acd*xd(k*tsam) + bc*u(t)}
+##
+## @math{xd((k+1)*tsam) = adc*xc(k*tsam) + add*xd(k*tsam) + bd*u(k*tsam)}
+##
+## @math{yc(t)      = ccc*xc(t)      + ccd*xd(k*tsam) + dc*u(t)}
+##
+## @math{yd(k*tsam) = cdc*xc(k*tsam) + cdd*xd(k*tsam) + dd*u(k*tsam)}
+## @end ifinfo
+## @iftex
+## @tex
+## $$\eqalign{
+## {d \over dt} x_c(t)
+##   & =   a_{cc} x_c(t)      + a_{cd} x_d(k*t_{sam}) + bc*u(t) \cr
+## x_d((k+1)*t_{sam})
+##   & =   a_{dc} x_c(k t_{sam}) + a_{dd} x_d(k t_{sam}) + b_d u(k t_{sam}) \cr
+## y_c(t)
+##  & =  c_{cc} x_c(t) + c_{cd} x_d(k t_{sam}) + d_c u(t) \cr
+## y_d(k t_{sam})
+##   & =  c_{dc} x_c(k t_{sam}) + c_{dd} x_d(k t_{sam}) + d_d u(k t_{sam})
+## }$$
+## @end tex
+## @end iftex
+##
+## @strong{Signal partitions}
+## @example
+## @group
+##         | continuous      | discrete               |
+## ----------------------------------------------------
+## states  | stname(1:n,:)   | stname((n+1):(n+nz),:) |
+## ----------------------------------------------------
+## outputs | outname(cout,:) | outname(outlist,:)     |
+## ----------------------------------------------------
+## @end group
+## @end example
+## where @math{cout} is the list of in 1:@code{rows}(@var{p})
+## that are not contained in outlist. (Discrete/continuous outputs
+## may be entered in any order desired by the user.)
+##
+## @strong{Example}
+## @example
+## octave:1> a = [1 2 3; 4 5 6; 7 8 10];
+## octave:2> b = [0 0 ; 0 1 ; 1 0];
+## octave:3> c = eye(3);
+## octave:4> sys = ss(a,b,c,[],0,3,0,list("volts","amps","joules"));
+## octave:5> sysout(sys);
+## Input(s)
+##         1: u_1
+##         2: u_2
+##
+## Output(s):
+##         1: y_1
+##         2: y_2
+##         3: y_3
+##
+## state-space form:
+## 3 continuous states, 0 discrete states
+## State(s):
+##         1: volts
+##         2: amps
+##         3: joules
+##
+## A matrix: 3 x 3
+##    1   2   3
+##    4   5   6
+##    7   8  10
+## B matrix: 3 x 2
+##   0  0
+##   0  1
+##   1  0
+## C matrix: 3 x 3
+##   1  0  0
+##   0  1  0
+##   0  0  1
+## D matrix: 3 x 3
+##   0  0
+##   0  0
+##   0  0
+## @end example
+## Notice that the @math{D} matrix is constructed  by default to the
+## correct dimensions.  Default input and output signals names were assigned
+## since none were given.
+## @end deftypefn
+
+## Author: John Ingram <ingraje@eng.auburn.edu>
+## Created: July 20, 1996
+
+function retsys = ss (a, b, c, d, tsam, n, nz, stname, inname, outname, outlist)
+
+  ## Test for correct number of inputs
+  if ((nargin < 3) | (nargin > 11))
+    usage("retsys = ss  (a,b,c{,d,tsam,n,nz,stname,inname,outname,outlist})");
+  endif
+
+  ## verify A, B, C, D arguments
+  ## If D is not specified, set it to a zero matrix of appriate dimension.
+  if (nargin == 3)          d = zeros(rows(c) , columns(b));
+  elseif (isempty(d))       d = zeros(rows(c) , columns(b));      endif
+
+  ## Check the dimensions
+  [na,m,p] = abcddim(a,b,c,d);
+
+  ## If dimensions are wrong, exit function
+  if (m == -1)
+    error("a(%dx%d), b(%dx%d), c(%dx%d), d(%dx%d); incompatible", ...
+      rows(a), columns(a), rows(b), columns(b), rows(c), columns(c), ...
+      rows(d), columns(d));
+  endif
+
+  ## check for tsam input
+  if(nargin < 5) tsam = 0;
+  elseif( !( is_sample(tsam) | (tsam == 0) ) )
+    error("tsam must be a nonnegative real scalar");
+  endif
+
+  ## check for continuous states
+  if( (nargin < 6) & (tsam == 0) )               n = na;
+  elseif(nargin < 6)                             n = 0;
+  elseif((!ismatrix(n)) | isstr(n))
+    error("Parameter n is not a numerical value.");
+  elseif( (!isscalar(n)) | (n < 0 ) | (n != round(n)) )
+    if(isscalar(n))     error("invalid value of n=%d,%e",n,n);
+    else                 error("invalid value of n=(%dx%d)", ...
+                           rows(n), columns(n));                endif
+  endif
+
+  ## check for num discrete states
+  if( (nargin < 7) & (tsam == 0))               nz = 0;
+  elseif(nargin < 7)                            nz = na - n;
+  elseif((!ismatrix(nz)) | isstr(nz))
+    error("Parameter nz is not a numerical value.");
+  elseif( (!isscalar(nz)) | (nz < 0 ) | (nz != round(nz)) )
+    if(isscalar(nz))
+      error(["invalid value of nz=",num2str(nz)]);
+    else
+      error(["invalid value of nz=(",num2str(rows(nz)),"x", ...
+        num2str(columns(nz)),")"]);
+    endif
+  endif
+
+  ## check for total number of states
+  if( (n + nz) != na )
+    error(["invalid: a is ",num2str(na),"x",num2str(na),", n=", ...
+        num2str(n),", nz=",num2str(nz)]);
+  endif
+
+  ## construct system with default names
+  retsys.a = a;
+  retsys.b = b;
+  retsys.c = c;
+  retsys.d = d;
+
+  retsys.n = n;
+  retsys.nz = nz;
+  retsys.tsam = tsam;
+  retsys.yd = zeros(1,p);     # default value entered below
+
+  ## Set the system vector:  active = 2(ss), updated = [0 0 1];
+  retsys.sys = [2, 0, 0, 1];
+
+  retsys.stname = __sysdefstname__ (n, nz);
+  retsys.inname = __sysdefioname__ (m, "u");
+  retsys.outname = __sysdefioname__ (p, "y");
+
+  ## check for state names
+  if(nargin >= 8)
+    if(!isempty(stname)) retsys = syssetsignals(retsys,"st",stname); endif
+  endif
+
+  ## check for input names
+  if(nargin >= 9)
+    if(!isempty(inname)) retsys = syssetsignals(retsys,"in",inname); endif
+  endif
+
+  ## check for output names
+  if(nargin >= 10)
+    if(!isempty(outname)) retsys = syssetsignals(retsys,"out",outname); endif
+  endif
+
+  ## set up yd
+  if(nargin < 11)
+    retsys = syssetsignals(retsys,"yd",ones(1,p)*(tsam > 0));
+  else
+    if(!isempty(outlist))
+      retsys = syssetsignals(retsys,"yd",ones(size(outlist)),outlist);
+    endif
+  endif
+
+endfunction
diff -r 567c8e2d2438 -r f105000ab25c scripts/control/system/tf.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/control/system/tf.m	Tue Feb 17 02:34:33 2004 +0000
@@ -0,0 +1,143 @@
+## 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} {} tf (@var{num}, @var{den}, @var{tsam}, @var{inname}, @var{outname})
+## build system data structure from transfer function format data
+##
+## @strong{Inputs}
+## @table @var
+## @item  num
+## @itemx den
+## coefficients of numerator/denominator polynomials
+## @item tsam
+## sampling interval. default: 0 (continuous time)
+## @item inname
+## @itemx outname
+## input/output signal names; may be a string or cell array with a single string
+## entry.
+## @end table
+##
+## @strong{Outputs}
+## @var{sys} = system data structure
+##
+## @strong{Example}
+## @example
+## octave:1> sys=tf([2 1],[1 2 1],0.1);
+## octave:2> sysout(sys)
+## Input(s)
+##         1: u_1
+## Output(s):
+##         1: y_1 (discrete)
+## Sampling interval: 0.1
+## transfer function form:
+## 2*z^1 + 1
+## -----------------
+## 1*z^2 + 2*z^1 + 1
+## @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
+
+function outsys = tf (num, den, tsam, inname, outname)
+
+  ## Test for the correct number of input arguments
+  if ((nargin < 2) || (nargin > 5))
+    usage ("outsys = tf (num, den [, tsam, inname, outname])");
+    return
+  endif
+
+  ## check input format
+  if( ! ( (isvector(num) || isscalar(num)) && ...
+        (isvector(den) || isscalar(den))) )
+    error(["num (",num2str(rows(num)),"x",num2str(columns(num)), ...
+      ") and den (",num2str(rows(den)),"x",num2str(columns(den)), ...
+      ") must be vectors"])
+  endif
+
+  ## strip leading zero coefficients
+  num = __tfl__ (num);
+  den = __tfl__ (den);
+
+  if (length(num) >  length(den))
+    error("# of poles (%d) < # of zeros (%d)",length(den)-1, length(num)-1);
+  endif
+
+  ## check sampling interval (if any)
+  if(nargin <= 2)           tsam = 0;           # default
+  elseif (isempty(tsam))    tsam = 0;           endif
+  if ( (! (isscalar(tsam) && (imag(tsam) == 0) )) || (tsam < 0) )
+    error("tsam must be a positive real scalar")
+  endif
+
+  outsys.num = num;
+  outsys.den = den;
+
+  ## Set the system vector:  active = 0(tf), updated = [1 0 0];
+  outsys.sys = [0, 1, 0, 0];
+
+  ## Set defaults
+  outsys.tsam = tsam;
+  outsys.n = length(den)-1;
+  outsys.nz = 0;
+  outsys.yd = 0;        # assume discrete-time
+  ## check discrete time
+  if(tsam > 0)
+    [outsys.n,outsys.nz] = swap(outsys.n, outsys.nz);
+    outsys.yd = 1;
+  endif
+
+  outsys.inname  = __sysdefioname__ (1, "u");
+  outsys.outname = __sysdefioname__ (1, "y");
+  outsys.stname  = __sysdefstname__ (outsys.n, outsys.nz);
+
+  ## Set name of input
+  if (nargin > 3)
+    ## make sure it's a cell array of a single string
+    if(!isempty(inname))
+      if(!iscell(inname))  inname = {inname};  endif
+      if( !is_signal_list(inname) )
+        error("inname must be a string or cell array of strings");
+      endif
+      if(length(inname) > 1)
+        warning("tf: %d input names provided; first used",length(inname));
+        inname = inname(1);
+      endif
+      outsys = syssetsignals(outsys,"in",inname);
+    endif
+  endif
+
+  ## Set name of output
+  if (nargin > 4)
+    if(!isempty(outname))
+      if(!iscell(outname))  outname = {outname};  endif
+      if(!is_signal_list(outname))
+        error("outname must be a string or a cell array of strings");
+      endif
+      if(length(outname) > 1)
+        warning("tf: %d output names provided; first used",length(outname));
+        outname = outname(1);
+      endif
+      outsys = syssetsignals(outsys,"out",outname);
+    endif
+  endif
+
+endfunction
diff -r 567c8e2d2438 -r f105000ab25c scripts/control/system/zp.m
--- /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