# HG changeset patch
# User jwe
# Date 939747186 0
# Node ID 6dd06d525de6fcc08bcbae1f96ad1691f5767306
# Parent  9c9f0c03530971f24142fc4f514c8b3e2c0a28d9
[project @ 1999-10-12 16:52:40 by jwe]

diff --git a/scripts/control/DEMOcontrol.m b/scripts/control/DEMOcontrol.m
--- a/scripts/control/DEMOcontrol.m
+++ b/scripts/control/DEMOcontrol.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel
+# Copyright (C) 1996 Auburn University. All rights reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/abcddim.m b/scripts/control/abcddim.m
--- a/scripts/control/abcddim.m
+++ b/scripts/control/abcddim.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved.
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/abcddims.m b/scripts/control/abcddims.m
--- a/scripts/control/abcddims.m
+++ b/scripts/control/abcddims.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1997 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/analdemo.m b/scripts/control/analdemo.m
--- a/scripts/control/analdemo.m
+++ b/scripts/control/analdemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/are.m b/scripts/control/are.m
--- a/scripts/control/are.m
+++ b/scripts/control/are.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/axis2dlim.m b/scripts/control/axis2dlim.m
--- a/scripts/control/axis2dlim.m
+++ b/scripts/control/axis2dlim.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/bddemo.m b/scripts/control/bddemo.m
--- a/scripts/control/bddemo.m
+++ b/scripts/control/bddemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/bode.m b/scripts/control/bode.m
--- a/scripts/control/bode.m
+++ b/scripts/control/bode.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/bode_bounds.m b/scripts/control/bode_bounds.m
--- a/scripts/control/bode_bounds.m
+++ b/scripts/control/bode_bounds.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/bodquist.m b/scripts/control/bodquist.m
--- a/scripts/control/bodquist.m
+++ b/scripts/control/bodquist.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/com2str.m b/scripts/control/com2str.m
--- a/scripts/control/com2str.m
+++ b/scripts/control/com2str.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/controldemo.m b/scripts/control/controldemo.m
--- a/scripts/control/controldemo.m
+++ b/scripts/control/controldemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/d2c.m b/scripts/control/d2c.m
--- a/scripts/control/d2c.m
+++ b/scripts/control/d2c.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/dare.m b/scripts/control/dare.m
--- a/scripts/control/dare.m
+++ b/scripts/control/dare.m
@@ -1,4 +1,4 @@
-## Copyright (C) 1996, 1997 John W. Eaton
+## Copyright (C) 1996, 1997 Auburn University.  All Rights Reserved.
 ##
 ## This file is part of Octave.
 ##
diff --git a/scripts/control/demomarsyas.m b/scripts/control/demomarsyas.m
--- a/scripts/control/demomarsyas.m
+++ b/scripts/control/demomarsyas.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/dgkfdemo.m b/scripts/control/dgkfdemo.m
--- a/scripts/control/dgkfdemo.m
+++ b/scripts/control/dgkfdemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/dgram.m b/scripts/control/dgram.m
--- a/scripts/control/dgram.m
+++ b/scripts/control/dgram.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/dlqe.m b/scripts/control/dlqe.m
--- a/scripts/control/dlqe.m
+++ b/scripts/control/dlqe.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved.
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/dlqg.m b/scripts/control/dlqg.m
--- a/scripts/control/dlqg.m
+++ b/scripts/control/dlqg.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/dlqr.m b/scripts/control/dlqr.m
--- a/scripts/control/dlqr.m
+++ b/scripts/control/dlqr.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved.
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/dlyap.m b/scripts/control/dlyap.m
--- a/scripts/control/dlyap.m
+++ b/scripts/control/dlyap.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved.
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/dmr2d.m b/scripts/control/dmr2d.m
--- a/scripts/control/dmr2d.m
+++ b/scripts/control/dmr2d.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. S. Hodel
+# Copyright (C) 1998 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/dre.m b/scripts/control/dre.m
--- a/scripts/control/dre.m
+++ b/scripts/control/dre.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel
+# Copyright (C) 1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/fir2sys.m b/scripts/control/fir2sys.m
--- a/scripts/control/fir2sys.m
+++ b/scripts/control/fir2sys.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/frdemo.m b/scripts/control/frdemo.m
--- a/scripts/control/frdemo.m
+++ b/scripts/control/frdemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/freqchkw.m b/scripts/control/freqchkw.m
--- a/scripts/control/freqchkw.m
+++ b/scripts/control/freqchkw.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/freqresp.m b/scripts/control/freqresp.m
--- a/scripts/control/freqresp.m
+++ b/scripts/control/freqresp.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/gram.m b/scripts/control/gram.m
--- a/scripts/control/gram.m
+++ b/scripts/control/gram.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/h2norm.m b/scripts/control/h2norm.m
--- a/scripts/control/h2norm.m
+++ b/scripts/control/h2norm.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/h2syn.m b/scripts/control/h2syn.m
--- a/scripts/control/h2syn.m
+++ b/scripts/control/h2syn.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/hinf_ctr.m b/scripts/control/hinf_ctr.m
--- a/scripts/control/hinf_ctr.m
+++ b/scripts/control/hinf_ctr.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/hinfnorm.m b/scripts/control/hinfnorm.m
--- a/scripts/control/hinfnorm.m
+++ b/scripts/control/hinfnorm.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/hinfsyn.m b/scripts/control/hinfsyn.m
--- a/scripts/control/hinfsyn.m
+++ b/scripts/control/hinfsyn.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/hinfsyn_chk.m b/scripts/control/hinfsyn_chk.m
--- a/scripts/control/hinfsyn_chk.m
+++ b/scripts/control/hinfsyn_chk.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/hinfsyn_ric.m b/scripts/control/hinfsyn_ric.m
--- a/scripts/control/hinfsyn_ric.m
+++ b/scripts/control/hinfsyn_ric.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/impulse.m b/scripts/control/impulse.m
--- a/scripts/control/impulse.m
+++ b/scripts/control/impulse.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/is_controllable.m b/scripts/control/is_controllable.m
--- a/scripts/control/is_controllable.m
+++ b/scripts/control/is_controllable.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/is_detectable.m b/scripts/control/is_detectable.m
--- a/scripts/control/is_detectable.m
+++ b/scripts/control/is_detectable.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/is_dgkf.m b/scripts/control/is_dgkf.m
--- a/scripts/control/is_dgkf.m
+++ b/scripts/control/is_dgkf.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/is_digital.m b/scripts/control/is_digital.m
--- a/scripts/control/is_digital.m
+++ b/scripts/control/is_digital.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996, 1999 A. Scottedward Hodel 
+# Copyright (C) 1996, 1999 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
@@ -36,7 +36,7 @@
   switch(nargin)
   case(1),  eflg = 0;
   case(2),  
-    if( isempty(find(eflg == [0 1 2])) )
+    if( isempty(find(eflg == [0, 1, 2])) )
       error("Illegal value of eflg=%d (%e)",eflg,eflg);
     endif
   otherwise,
diff --git a/scripts/control/is_observable.m b/scripts/control/is_observable.m
--- a/scripts/control/is_observable.m
+++ b/scripts/control/is_observable.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/is_sample.m b/scripts/control/is_sample.m
--- a/scripts/control/is_sample.m
+++ b/scripts/control/is_sample.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/is_signal_list.m b/scripts/control/is_signal_list.m
--- a/scripts/control/is_signal_list.m
+++ b/scripts/control/is_signal_list.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/is_siso.m b/scripts/control/is_siso.m
--- a/scripts/control/is_siso.m
+++ b/scripts/control/is_siso.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/is_stabilizable.m b/scripts/control/is_stabilizable.m
--- a/scripts/control/is_stabilizable.m
+++ b/scripts/control/is_stabilizable.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/is_stable.m b/scripts/control/is_stable.m
--- a/scripts/control/is_stable.m
+++ b/scripts/control/is_stable.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/lqe.m b/scripts/control/lqe.m
--- a/scripts/control/lqe.m
+++ b/scripts/control/lqe.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/lqg.m b/scripts/control/lqg.m
--- a/scripts/control/lqg.m
+++ b/scripts/control/lqg.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996, 1997 A. Scottedward Hodel 
+# Copyright (C) 1996, 1997 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/lqr.m b/scripts/control/lqr.m
--- a/scripts/control/lqr.m
+++ b/scripts/control/lqr.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993, 1994, 1995 John W. Eaton
+# Copyright (C) 1993, 1994, 1995 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
diff --git a/scripts/control/lsim.m b/scripts/control/lsim.m
--- a/scripts/control/lsim.m
+++ b/scripts/control/lsim.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/ltifr.m b/scripts/control/ltifr.m
--- a/scripts/control/ltifr.m
+++ b/scripts/control/ltifr.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/lyap.m b/scripts/control/lyap.m
--- a/scripts/control/lyap.m
+++ b/scripts/control/lyap.m
@@ -1,4 +1,4 @@
-## Copyright (C) 1996, 1997 John W. Eaton
+## Copyright (C) 1996, 1997 Auburn University.  All Rights Reserved
 ##
 ## This file is part of Octave.
 ##
diff --git a/scripts/control/mb.m b/scripts/control/mb.m
--- a/scripts/control/mb.m
+++ b/scripts/control/mb.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/minfo.m b/scripts/control/minfo.m
--- a/scripts/control/minfo.m
+++ b/scripts/control/minfo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/moddemo.m b/scripts/control/moddemo.m
--- a/scripts/control/moddemo.m
+++ b/scripts/control/moddemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/nichols.m b/scripts/control/nichols.m
--- a/scripts/control/nichols.m
+++ b/scripts/control/nichols.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/nyquist.m b/scripts/control/nyquist.m
--- a/scripts/control/nyquist.m
+++ b/scripts/control/nyquist.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/outlist.m b/scripts/control/outlist.m
--- a/scripts/control/outlist.m
+++ b/scripts/control/outlist.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996, 1998 A. Scottedward Hodel 
+# Copyright (C) 1996, 1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/packedform.m b/scripts/control/packedform.m
--- a/scripts/control/packedform.m
+++ b/scripts/control/packedform.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/packsys.m b/scripts/control/packsys.m
--- a/scripts/control/packsys.m
+++ b/scripts/control/packsys.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/parallel.m b/scripts/control/parallel.m
--- a/scripts/control/parallel.m
+++ b/scripts/control/parallel.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/polyout.m b/scripts/control/polyout.m
--- a/scripts/control/polyout.m
+++ b/scripts/control/polyout.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1995,1998 A. Scottedward Hodel
+# Copyright (C) 1995,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/prompt.m b/scripts/control/prompt.m
--- a/scripts/control/prompt.m
+++ b/scripts/control/prompt.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/pzmap.m b/scripts/control/pzmap.m
--- a/scripts/control/pzmap.m
+++ b/scripts/control/pzmap.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/qzval.m b/scripts/control/qzval.m
--- a/scripts/control/qzval.m
+++ b/scripts/control/qzval.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/rldemo.m b/scripts/control/rldemo.m
--- a/scripts/control/rldemo.m
+++ b/scripts/control/rldemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/rlocus.m b/scripts/control/rlocus.m
--- a/scripts/control/rlocus.m
+++ b/scripts/control/rlocus.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/rotg.m b/scripts/control/rotg.m
--- a/scripts/control/rotg.m
+++ b/scripts/control/rotg.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/run_cmd.m b/scripts/control/run_cmd.m
--- a/scripts/control/run_cmd.m
+++ b/scripts/control/run_cmd.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/series.m b/scripts/control/series.m
--- a/scripts/control/series.m
+++ b/scripts/control/series.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sortcom.m b/scripts/control/sortcom.m
--- a/scripts/control/sortcom.m
+++ b/scripts/control/sortcom.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/ss2sys.m b/scripts/control/ss2sys.m
--- a/scripts/control/ss2sys.m
+++ b/scripts/control/ss2sys.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
@@ -105,6 +105,8 @@
   # check for continuous states
   if( (nargin < 6) & (tsam == 0) )               n = na;
   elseif(nargin < 6)                             n = 0;
+  elseif((!is_matrix(n)) | isstr(n))
+    error("Parameter n is not a numerical value.");
   elseif( (!is_scalar(n)) | (n < 0 ) | (n != round(n)) )
     if(is_scalar(n))     error("illegal value of n=%d,%e",n,n);
     else                 error("illegal value of n=(%dx%d)", ...
@@ -114,6 +116,8 @@
   # check for num discrete states
   if( (nargin < 7) & (tsam == 0)) 		nz = 0;
   elseif(nargin < 7)				nz = na - n;
+  elseif((!is_matrix(nz)) | isstr(nz))
+    error("Parameter nz is not a numerical value.");
   elseif( (!is_scalar(nz)) | (nz < 0 ) | (nz != round(nz)) )
     if(is_scalar(nz))
       error(["illegal value of nz=",num2str(nz)]);
diff --git a/scripts/control/ss2tf.m b/scripts/control/ss2tf.m
--- a/scripts/control/ss2tf.m
+++ b/scripts/control/ss2tf.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/ss2zp.m b/scripts/control/ss2zp.m
--- a/scripts/control/ss2zp.m
+++ b/scripts/control/ss2zp.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/starp.m b/scripts/control/starp.m
--- a/scripts/control/starp.m
+++ b/scripts/control/starp.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/step.m b/scripts/control/step.m
--- a/scripts/control/step.m
+++ b/scripts/control/step.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/stepimp.m b/scripts/control/stepimp.m
--- a/scripts/control/stepimp.m
+++ b/scripts/control/stepimp.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/strappend.m b/scripts/control/strappend.m
--- a/scripts/control/strappend.m
+++ b/scripts/control/strappend.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/susball.m b/scripts/control/susball.m
--- a/scripts/control/susball.m
+++ b/scripts/control/susball.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/swap.m b/scripts/control/swap.m
--- a/scripts/control/swap.m
+++ b/scripts/control/swap.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/swapcols.m b/scripts/control/swapcols.m
--- a/scripts/control/swapcols.m
+++ b/scripts/control/swapcols.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/swaprows.m b/scripts/control/swaprows.m
--- a/scripts/control/swaprows.m
+++ b/scripts/control/swaprows.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sys2fir.m b/scripts/control/sys2fir.m
--- a/scripts/control/sys2fir.m
+++ b/scripts/control/sys2fir.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sys2ss.m b/scripts/control/sys2ss.m
--- a/scripts/control/sys2ss.m
+++ b/scripts/control/sys2ss.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996, 1998 A. Scottedward Hodel 
+# Copyright (C) 1996, 1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sys2tf.m b/scripts/control/sys2tf.m
--- a/scripts/control/sys2tf.m
+++ b/scripts/control/sys2tf.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sys2zp.m b/scripts/control/sys2zp.m
--- a/scripts/control/sys2zp.m
+++ b/scripts/control/sys2zp.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysadd.m b/scripts/control/sysadd.m
--- a/scripts/control/sysadd.m
+++ b/scripts/control/sysadd.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996,1999 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
@@ -16,16 +16,16 @@
 # along with Octave; see the file COPYING.  If not, write to the Free 
 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
  
-function sys = sysadd(Gsys,Hsys)
+function sys = sysadd(...)
 # 
-# [sys] = sysadd(Gsys,Hsys)
-#
+# sys = sysadd(Gsys{,Hsys,...})
 #
-# returns transfer function sys = Gsys + Hsys
+# returns transfer function sys = Gsys + Hsys + ...
 #
-# Method: Gsys and Hsys are connected in parallel
-# The vector are connected to both systems; the outputs will be 
-# added.  The names given to the system will be the G systems names.
+# Method: sysgroup used to connect systems in parallel
+# The input vector is connected to all systems; the outputs are summed.
+# Returned system input/output signal names are those of Gsys.  For
+# example, sysadd(Gsys,Hsys) results in
 #
 #                  ________
 #             ----|  Gsys  |---
@@ -36,62 +36,78 @@
 #                  --------
 
 # Written by John Ingram July 1996
+# Updated for variable number of arguments July 1999 A. S. Hodel
 
   save_val = implicit_str_to_num_ok;	# save for later
   implicit_str_to_num_ok = 1;
 
-  if(nargin != 2)
-    usage("sysadd:  [sys] = sysysadd(Gsys,Hsys)");
-  endif
-
-  # check inputs
-  if(!is_struct(Gsys) | !is_struct(Hsys))
-    error("Both Gsys and Hsys must be in system data structure form");
-  endif
-
-  # check for compatibility
-  [n,nz,mg,pg] = sysdimensions(Gsys);
-  [n,nz,mh,ph] = sysdimensions(Hsys);
-  if(mg != mh)
-    error(sprintf("Gsys inputs(%d) != Hsys inputs (%d)",mg,mh));
-  elseif(pg != ph)
-    error(sprintf("Gsys outputs(%d) != Hsys outputs (%d)",pg,ph));
-  endif
-
-  [Gst, Gin, Gout, Gyd] = sysgetsignals(Gsys);
-  [Hst, Hin, Hout, Hyd] = sysgetsignals(Hsys);
-
-  # check for digital to continuous addition
-  if (Gyd != Hyd)
-    error("can not add a discrete output to a continuous output");
+  if(nargin < 1)
+    usage("sysadd: sys = sysysadd(Gsys{,Hsys, ...})");
   endif
 
-  if( strcmp(sysgettype(Gsys),"tf") | strcmp(sysgettype(Hsys),"tf") )
-    # see if adding  transfer functions with identical denominators
-    [Gnum,Gden,GT,Gin,Gout] = sys2tf(Gsys);
-    [Hnum,Hden,HT,Hin,Hout] = sys2tf(Hsys);
-    if( (Hden == Gden) & (HT == GT) )
-      sys = tf2sys(Gnum+Hnum,Gden,GT,Gin,Gout);
-      return
+  # collect all arguments
+  arglist = list();
+  va_start();
+  for kk=1:nargin
+    arglist(kk) = va_arg();
+    if(!is_struct(nth(arglist,kk)))
+      error("sysadd: argument %d is not a data structure",kk);
     endif
-    # if not, we go on and do the usual thing...
-  endif
+  endfor
 
-  # make sure in ss form
-  Gsys = sysupdate(Gsys,"ss");
-  Hsys = sysupdate(Hsys,"ss");
+  # check system dimensions
+  [n,nz,mg,pg,Gyd] = sysdimensions(nth(arglist,1));
+  for kk=2:nargin
+    [n,nz,mh,ph,Hyd] = sysdimensions(nth(arglist,kk));
+    if(mg != mh)
+      error("arg 1 has %d inputs; arg %d has vs %d inputs",mg,kk,mh);
+    elseif(pg != ph)
+      error("arg 1 has %d outputs; arg %d has vs %d outputs",pg,kk,ph);
+    elseif(norm(Gyd - Hyd))
+      warning("cannot add a discrete output to a continuous output");
+      error("Output type mismatch: arguments 1 and %d\n",kk);
+    endif
+  endfor
 
-  # change signal names to avoid warning messages from sysgroup
-  Gsys = syssetsignals(Gsys,"in",sysdefioname(length(Gin),"Gin_u"));
-  Gsys = syssetsignals(Gsys,"out",sysdefioname(length(Gout),"Gout_u"));
-  Hsys = syssetsignals(Hsys,"in",sysdefioname(length(Hin),"Hin_u"));
-  Hsys = syssetsignals(Hsys,"out",sysdefioname(length(Hout),"Hout_u"));
+  # perform the add
+  if(nargin == 2)
+    Gsys = nth(arglist,1);   Hsys = nth(arglist,2);
+    if( strcmp(sysgettype(Gsys),"tf") | strcmp(sysgettype(Hsys),"tf") )
+      # see if adding  transfer functions with identical denominators
+      [Gnum,Gden,GT,Gin,Gout] = sys2tf(Gsys);
+      [Hnum,Hden,HT,Hin,Hout] = sys2tf(Hsys);
+      if(length(Hden) == length(Gden) )
+        if( (Hden == Gden) & (HT == GT) )
+          sys = tf2sys(Gnum+Hnum,Gden,GT,Gin,Gout);
+          return
+        endif
+        # if not, we go on and do the usual thing...
+      endif
+    endif
+  
+    # make sure in ss form
+    Gsys = sysupdate(Gsys,"ss");
+    Hsys = sysupdate(Hsys,"ss");
   
-  sys = sysgroup(Gsys,Hsys);
+    # change signal names to avoid warning messages from sysgroup
+    Gsys = syssetsignals(Gsys,"in",sysdefioname(length(Gin),"Gin_u"));
+    Gsys = syssetsignals(Gsys,"out",sysdefioname(length(Gout),"Gout_u"));
+    Hsys = syssetsignals(Hsys,"in",sysdefioname(length(Hin),"Hin_u"));
+    Hsys = syssetsignals(Hsys,"out",sysdefioname(length(Hout),"Hout_u"));
+    
+    sys = sysgroup(Gsys,Hsys);
+  
+    eyin = eye(mg);
+    eyout = eye(pg);
+  
+    sys = sysscale(sys,[eyout, eyout],[eyin;eyin],Gout,Gin);
+  
+  else
+    # multiple systems (or a single system); combine together one by one
+    sys = nth(arglist,1);
+    for kk=2:length(arglist)
+      sys = sysadd(sys,nth(arglist,kk));
+    endfor
+  endif
+endfunction
 
-  eyin = eye(mg);
-  eyout = eye(pg);
-
-  sys = sysscale(sys,[eyout, eyout],[eyin;eyin],Gout,Gin);
-
-endfunction
diff --git a/scripts/control/sysappend.m b/scripts/control/sysappend.m
--- a/scripts/control/sysappend.m
+++ b/scripts/control/sysappend.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/syschnames.m b/scripts/control/syschnames.m
--- a/scripts/control/syschnames.m
+++ b/scripts/control/syschnames.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/syschnamesl.m b/scripts/control/syschnamesl.m
--- a/scripts/control/syschnamesl.m
+++ b/scripts/control/syschnamesl.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
@@ -25,8 +25,17 @@
   #
   # combines the two string lists old_names and inames
 
-  # $Revision: 1.2 $
+  # $Revision: 2.1.14.5 $
   # $Log: syschnamesl.m,v $
+# Revision 2.1.14.5  1999/09/22  21:55:46  scotte
+# Auburn copyright fixed; krylov.m patched to fix bug
+#
+# Revision 2.1.14.4  1999/07/21  19:49:21  scotte
+# sysgroup, sysadd, sysmult, syssub accept variable # of input args
+#
+  # Revision 1.3  1998/07/17 15:08:50  hodelas
+  # use isempty instead of max(size(...))
+  #
   # Revision 1.2  1998/07/01 16:23:39  hodelas
   # Updated c2d, d2c to perform bilinear transforms.
   # Updated several files per bug updates from users.
diff --git a/scripts/control/syschtsam.m b/scripts/control/syschtsam.m
--- a/scripts/control/syschtsam.m
+++ b/scripts/control/syschtsam.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysconnect.m b/scripts/control/sysconnect.m
--- a/scripts/control/sysconnect.m
+++ b/scripts/control/sysconnect.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/syscont.m b/scripts/control/syscont.m
--- a/scripts/control/syscont.m
+++ b/scripts/control/syscont.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/syscont_disc.m b/scripts/control/syscont_disc.m
--- a/scripts/control/syscont_disc.m
+++ b/scripts/control/syscont_disc.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysdefioname.m b/scripts/control/sysdefioname.m
--- a/scripts/control/sysdefioname.m
+++ b/scripts/control/sysdefioname.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysdefstname.m b/scripts/control/sysdefstname.m
--- a/scripts/control/sysdefstname.m
+++ b/scripts/control/sysdefstname.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysdimensions.m b/scripts/control/sysdimensions.m
--- a/scripts/control/sysdimensions.m
+++ b/scripts/control/sysdimensions.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/sysdisc.m b/scripts/control/sysdisc.m
--- a/scripts/control/sysdisc.m
+++ b/scripts/control/sysdisc.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysdup.m b/scripts/control/sysdup.m
--- a/scripts/control/sysdup.m
+++ b/scripts/control/sysdup.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysgetsignals.m b/scripts/control/sysgetsignals.m
--- a/scripts/control/sysgetsignals.m
+++ b/scripts/control/sysgetsignals.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysgettsam.m b/scripts/control/sysgettsam.m
--- a/scripts/control/sysgettsam.m
+++ b/scripts/control/sysgettsam.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave.
 #
diff --git a/scripts/control/sysgettype.m b/scripts/control/sysgettype.m
--- a/scripts/control/sysgettype.m
+++ b/scripts/control/sysgettype.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1998 A. Scottedward Hodel 
+# Copyright (C) 1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysgroup.m b/scripts/control/sysgroup.m
--- a/scripts/control/sysgroup.m
+++ b/scripts/control/sysgroup.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996, 1998, 1999 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
@@ -16,12 +16,15 @@
 # along with Octave; see the file COPYING.  If not, write to the Free 
 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
  
-function sys = sysgroup(Asys,Bsys)
-# function sys = sysgroup(Asys,Bsys)
-# Combines two system data structures into a single system
+function sys = sysgroup(...)
+# function sys = sysgroup(Asys{,Bsys,...})
+# Parallel connection of systems
 #
-# input: Asys, Bsys: system data structures
-# output: sys: Asys and Bsys are combined into a single system:
+# inputs: All input arguments must be system data structures;
+#         exits with an error if there is not at least one argument
+# output: sys: all systems are combined into a single system; e.g.,
+#         if two systems are passed as sysgroup(Asys,Bsys), the result
+#         is
 #
 #              __________________
 #              |    ________    |
@@ -36,10 +39,11 @@
 # The function also rearranges the A,B,C matrices so that the 
 # continuous states come first and the discrete states come last.
 # If there are duplicate names, the second name has a unique suffix appended
-# on to the end of the name.
+# on to the end of the name (a warning message is printed).
 
 # A. S. Hodel August 1995
 # modified by John Ingram July 1996
+# A. S. Hodel: modified for variable number of arguments 1999
 
   save_val = implicit_str_to_num_ok;	# save for later
   implicit_str_to_num_ok = 1;
@@ -47,75 +51,98 @@
   save_emp = empty_list_elements_ok;
   empty_list_elements_ok = 1;
 
-  if(nargin ~= 2)
-    usage("sys = sysgroup(Asys,Bsys)");
-  elseif( !is_struct(Asys) | !is_struct(Bsys) )
-    error("sysgroup: input arguments must both be structured systems");
-  endif
-
-  # extract information from Asys, Bsys to consruct sys
-  Asys = sysupdate(Asys,"ss");
-  Bsys = sysupdate(Bsys,"ss");
-  [n1,nz1,m1,p1] = sysdimensions(Asys);
-  [n2,nz2,m2,p2] = sysdimensions(Bsys);
-  [Aa,Ab,Ac,Ad,Atsam,An,Anz,Ast,Ain,Aout,Ayd] = sys2ss(Asys);
-  [Ba,Bb,Bc,Bd,Btsam,Bn,Bnz,Bst,Bin,Bout,Byd] = sys2ss(Bsys);
-  nA = An + Anz;
-  nB = Bn + Bnz;
-
-  if(p1*m1*p2*m2 == 0)
-    error("sysgroup: argument lacks inputs and/or outputs");
-
-  elseif((Atsam + Btsam > 0) & (Atsam * Btsam == 0) )
-    warning("sysgroup: creating combination of continuous and discrete systems")
-
-  elseif(Atsam != Btsam)
-    error("sysgroup: Asys.tsam=%e, Bsys.tsam =%e", Atsam, Btsam);
+    
+  if(nargin < 1)
+    usage("sys = sysgroup(Asys{,Bsys,...})");
   endif
 
-  A = [Aa,zeros(nA,nB); zeros(nB,nA),Ba];
-  B = [Ab,zeros(nA,m2); zeros(nB,m1),Bb];
-  C = [Ac,zeros(p1,nB); zeros(p2,nA),Bc];
-  D = [Ad,zeros(p1,m2); zeros(p2,m1),Bd];
-  tsam = max(Atsam,Btsam);
-
-  # construct combined signal names; stnames must check for pure gain blocks
-  if(isempty(Ast))
-    stname = Bst;
-  elseif(isempty(Bst))
-    stname = Ast;
-  else
-    stname  = append(Ast, Bst);
-  endif
-  inname  = append(Ain, Bin);
-  outname = append(Aout,Bout);
+  # collect all arguments
+  arglist = list();
+  va_start();
+  for kk=1:nargin
+    arglist(kk) = va_arg();
+    if(!is_struct(nth(arglist,kk)))
+      error("sysgroup: argument %d is not a data structure",kk);
+    endif
+  endfor
 
-  # Sort states into continous first, then discrete
-  dstates = ones(1,(nA+nB));
-  if(An)
-    dstates(1:(An)) = zeros(1,An);
-  endif
-  if(Bn)
-    dstates((nA+1):(nA+Bn)) = zeros(1,Bn);
+  if(nargin == 2)
+    # the usual case; group the two systems together
+    Asys = nth(arglist,1);
+    Bsys = nth(arglist,2);
+  
+    # extract information from Asys, Bsys to consruct sys
+    Asys = sysupdate(Asys,"ss");
+    Bsys = sysupdate(Bsys,"ss");
+    [n1,nz1,m1,p1] = sysdimensions(Asys);
+    [n2,nz2,m2,p2] = sysdimensions(Bsys);
+    [Aa,Ab,Ac,Ad,Atsam,An,Anz,Ast,Ain,Aout,Ayd] = sys2ss(Asys);
+    [Ba,Bb,Bc,Bd,Btsam,Bn,Bnz,Bst,Bin,Bout,Byd] = sys2ss(Bsys);
+    nA = An + Anz;
+    nB = Bn + Bnz;
+  
+    if(p1*m1*p2*m2 == 0)
+      error("sysgroup: argument lacks inputs and/or outputs");
+  
+    elseif((Atsam + Btsam > 0) & (Atsam * Btsam == 0) )
+      warning("sysgroup: creating combination of continuous and discrete systems")
+  
+    elseif(Atsam != Btsam)
+      error("sysgroup: Asys.tsam=%e, Bsys.tsam =%e", Atsam, Btsam);
+    endif
+  
+    A = [Aa,zeros(nA,nB); zeros(nB,nA),Ba];
+    B = [Ab,zeros(nA,m2); zeros(nB,m1),Bb];
+    C = [Ac,zeros(p1,nB); zeros(p2,nA),Bc];
+    D = [Ad,zeros(p1,m2); zeros(p2,m1),Bd];
+    tsam = max(Atsam,Btsam);
+  
+    # construct combined signal names; stnames must check for pure gain blocks
+    if(isempty(Ast))
+      stname = Bst;
+    elseif(isempty(Bst))
+      stname = Ast;
+    else
+      stname  = append(Ast, Bst);
+    endif
+    inname  = append(Ain, Bin);
+    outname = append(Aout,Bout);
+  
+    # Sort states into continous first, then discrete
+    dstates = ones(1,(nA+nB));
+    if(An)
+      dstates(1:(An)) = zeros(1,An);
+    endif
+    if(Bn)
+      dstates((nA+1):(nA+Bn)) = zeros(1,Bn);
+    endif
+    [tmp,pv] = sort(dstates);
+    A = A(pv,pv);
+    B = B(pv,:);
+    C = C(:,pv);
+    stname = stname(pv);
+  
+    # check for duplicate signal names
+    inname = sysgroupn(inname,"input");
+    stname = sysgroupn(stname,"state");
+    outname = sysgroupn(outname,"output");
+  
+    # mark discrete outputs
+    outlist = find([Ayd, Byd]);
+  
+    # build new system
+    sys = ss2sys(A,B,C,D,tsam,An+Bn,Anz+Bnz,stname,inname,outname);
+
+  else
+    # multiple systems (or a single system); combine together one by one
+    sys = nth(arglist,1);
+    for kk=2:length(arglist)
+      printf("sysgroup: kk=%d\n",kk);
+      sys = sysgroup(sys,nth(arglist,kk));
+    endfor
   endif
-  [tmp,pv] = sort(dstates);
-  A = A(pv,pv);
-  B = B(pv,:);
-  C = C(:,pv);
-  stname = stname(pv);
-
-  # check for duplicate signal names
-  inname = sysgroupn(inname,"input");
-  stname = sysgroupn(stname,"state");
-  outname = sysgroupn(outname,"output");
-
-  # mark discrete outputs
-  outlist = find([Ayd, Byd]);
-
-  # build new system
-  sys = ss2sys(A,B,C,D,tsam,An+Bn,Anz+Bnz,stname,inname,outname);
-
+  
   implicit_str_to_num_ok = save_val;	# restore value  
   empty_list_elements_ok = save_emp;
-
+    
 endfunction
diff --git a/scripts/control/sysgroupn.m b/scripts/control/sysgroupn.m
--- a/scripts/control/sysgroupn.m
+++ b/scripts/control/sysgroupn.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved.
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysidx.m b/scripts/control/sysidx.m
--- a/scripts/control/sysidx.m
+++ b/scripts/control/sysidx.m
@@ -1,3 +1,24 @@
+# Copyright (C) 1999 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, 675 Mass Ave, Cambridge, MA 02139, USA.
+#
+# Written by A. S. Hodel, a.s.hodel@eng.auburn.edu
+
+
 function idxvec = sysidx(sys,sigtype,signamelist)
 # idxvec = sysidx(sys,sigtype,signamelist)
 # return indices of signals with specified signal names
diff --git a/scripts/control/sysmin.m b/scripts/control/sysmin.m
--- a/scripts/control/sysmin.m
+++ b/scripts/control/sysmin.m
@@ -1,3 +1,23 @@
+# 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, 675 Mass Ave, Cambridge, MA 02139, USA.
+#
+# Written by A. S. Hodel a.s.hodel@eng.auburn.edu
+
 function [retsys,nc,no,cflg,oflg] = sysmin(sys,flg);
   # [retsys,nc,no] = sysmin(sys{,flg});
   # return a minimal (or reduced order) system
diff --git a/scripts/control/sysmult.m b/scripts/control/sysmult.m
--- a/scripts/control/sysmult.m
+++ b/scripts/control/sysmult.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996,1999 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
@@ -16,14 +16,14 @@
 # along with Octave; see the file COPYING.  If not, write to the Free 
 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
  
-function [sys] = sysmult(Asys,Bsys)
+function sys = sysmult(...)
 #
-# [sys] = sysmult(Asys,Bsys)
+# sys = sysmult(Asys{,Bsys,...})
 #
-# returns sys = Asys*Bsys
+# returns transfer function sys = Asys*Bsys* ...
 #
-# This function takes two systems, Asys and Bsys, and multiplies them together.
-# This has the effect of connecting the outputs of Bsys to the inputs of Asys.
+# Same as series connection of systems; for example, sysmult(Asys,Bsys)
+# returns sys = Asys*Bsys with block diagram
 #
 #
 #     u   ----------     ----------
@@ -36,60 +36,82 @@
 # does not recognize discrete inputs)
 
 # Written by John Ingram July 1996
+# updated for variable number of arguments by A. S. Hodel July 1999
 
   save_val = implicit_str_to_num_ok;	# save for later
   implicit_str_to_num_ok = 1;
 
-  if(nargin != 2)
-    usage("sysmult:  [sys] = sysmult(Asys,Bsys)");
-  endif
-
-  # check inputs
-  if(!is_struct(Asys) | !is_struct(Bsys))
-    error("Both Asys and Bsys must be in system data structure form")
-  endif
-
-  # check for compatibility
-  [An,Anz,Am,Ap] = sysdimensions(Asys);
-  [Bn,Bnz,Bm,Bp] = sysdimensions(Bsys);
-  if(Bp != Am)
-    error(["Bsys has ",num2str(Bp)," outputs, Asys has ",num2str(Am), ...
-	" inputs; mismatch."]);
+  if(nargin < 1)
+    usage("sysmult: sys = sysmult(Asys{,Bsys,...})");
   endif
 
-  [Aa,Ab,Ac,Ad,Atsam,An,Anz,Astname,Ainname,Aoutname,Ayd] = sys2ss(Asys);
-  [Ba,Bb,Bc,Bd,Btsam,Bn,Bnz,Bstname,Binname,Boutname,Byd] = sys2ss(Bsys);
+  # collect all arguments
+  arglist = list();
+  va_start();
+  for kk=1:nargin
+    arglist(kk) = va_arg();
+    if(!is_struct(nth(arglist,kk)))
+      error("sysadd: argument %d is not a data structure",kk);
+    endif
+  endfor
+
+  # check system dimensions
+  [n,nz,mg,pg,Gyd] = sysdimensions(nth(arglist,1));
+  for kk=2:nargin
+    [n,nz,mh,ph,Hyd] = sysdimensions(nth(arglist,kk));
+    if(mh != pg)
+      error("arg %d has %d outputs; arg %d has vs %d inputs",kk,ph,kk-1,mg);
+    endif
+    [n,nz,mg,pg,Gyd] = sysdimensions(nth(arglist,kk));   # for next iteration
+  endfor
 
-  if(Byd)
-    # check direct feed-through of inputs through discrete outputs
-    alist = find(Byd);
-    if(An)
-      bd = Ab(1:An)* Bd(alist,:);	
-      if(norm(bd,1))
-        warning("sysmult: inputs -> Bsys discrete outputs -> continous states of Asys");
+  # perform the multiply
+  if(nargin == 2)
+    Asys = nth(arglist,1);   Bsys = nth(arglist,2);
+ 
+    [An,Anz,Am,Ap] = sysdimensions(Asys);
+    [Bn,Bnz,Bm,Bp] = sysdimensions(Bsys);
+
+    [Aa,Ab,Ac,Ad,Atsam,An,Anz,Astname,Ainname,Aoutname,Ayd] = sys2ss(Asys);
+    [Ba,Bb,Bc,Bd,Btsam,Bn,Bnz,Bstname,Binname,Boutname,Byd] = sys2ss(Bsys);
+  
+    if(Byd)
+      # check direct feed-through of inputs through discrete outputs
+      alist = find(Byd);
+      if(An)
+        bd = Ab(1:An)* Bd(alist,:);	
+        if(norm(bd,1))
+          warning("sysmult: inputs -> Bsys discrete outputs -> continous states of Asys");
+        endif
+      endif
+      # check direct feed-through of continuous state through discrete outputs
+      if(Bn)
+        bc = Ab(1:An)* Bc(alist,1:(Bn));	
+        if( norm(bc,1) )
+          warning("sysmult: Bsys states -> Bsys discrete outputs -> continuous states of Asys");
+        endif
       endif
     endif
-    # check direct feed-through of continuous state through discrete outputs
-    if(Bn)
-      bc = Ab(1:An)* Bc(alist,1:(Bn));	
-      if( norm(bc,1) )
-        warning("sysmult: Bsys states -> Bsys discrete outputs -> continuous states of Asys");
-      endif
-    endif
-  endif
+  
+    # change signal names to avoid spurious warnings from sysgroup
+    Asys = syssetsignals(Asys,"in",sysdefioname(Am,"A_sysmult_tmp_name"));
+    Bsys = syssetsignals(Bsys,"out",sysdefioname(Bp,"B_sysmult_tmp_name"));
+  
+    sys = sysgroup(Asys,Bsys);
+  
+    # connect outputs of B to inputs of A
+    sys = sysconnect(sys,Ap+(1:Bp),1:Am);
+   
+    # now keep only  outputs of A and inputs of B
+    sys = sysprune(sys,1:Ap,Am+(1:Bm));
 
-  # change signal names to avoid spurious warnings from sysgroup
-  Asys = syssetsignals(Asys,"in",sysdefioname(Am,"A_sysmult_tmp_name"));
-  Bsys = syssetsignals(Bsys,"out",sysdefioname(Bp,"B_sysmult_tmp_name"));
-
-  sys = sysgroup(Asys,Bsys);
-
-  # connect outputs of B to inputs of A
-  sys = sysconnect(sys,Ap+(1:Bp),1:Am);
- 
-  # now keep only  outputs of A and inputs of B
-  sys = sysprune(sys,1:Ap,Am+(1:Bm));
-
+  else
+    # multiple systems (or a single system); combine together one by one
+    sys = nth(arglist,1);
+    for kk=2:length(arglist)
+      sys = sysmult(sys,nth(arglist,kk));
+    endfor
+  endif
   implicit_str_to_num_ok = save_val;	# restore value  
 endfunction  
   
diff --git a/scripts/control/sysout.m b/scripts/control/sysout.m
--- a/scripts/control/sysout.m
+++ b/scripts/control/sysout.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysprune.m b/scripts/control/sysprune.m
--- a/scripts/control/sysprune.m
+++ b/scripts/control/sysprune.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysreorder.m b/scripts/control/sysreorder.m
--- a/scripts/control/sysreorder.m
+++ b/scripts/control/sysreorder.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysrepdemo.m b/scripts/control/sysrepdemo.m
--- a/scripts/control/sysrepdemo.m
+++ b/scripts/control/sysrepdemo.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/sysscale.m b/scripts/control/sysscale.m
--- a/scripts/control/sysscale.m
+++ b/scripts/control/sysscale.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/syssetsignals.m b/scripts/control/syssetsignals.m
--- a/scripts/control/syssetsignals.m
+++ b/scripts/control/syssetsignals.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/syssub.m b/scripts/control/syssub.m
--- a/scripts/control/syssub.m
+++ b/scripts/control/syssub.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996,1999 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
@@ -16,16 +16,18 @@
 # along with Octave; see the file COPYING.  If not, write to the Free 
 # Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
  
-function sys = syssub(Gsys,Hsys)
+function sys = syssub(...)
 # 
-# [sys] = syssub(Gsys,Hsys)
+# sys = syssub(Gsys{,Hsys, ...})
 #
+# returns transfer function sys = Gsys - Hsys - ...
 #
-# returns transfer functin sys = Gsys - Hsys
-#
-# Method: Gsys and Hsys are connected in parallel
-# The vector are connected to both systems; the outputs will be 
-# subtracted.  The names given to the system will be the G systems names.
+# Method: sysgroup used to connect systems in parallel
+# The input vector is connected to all systems; the outputs of all
+# systems are connected to a summing junction with the first system's
+# outputs added, all other outputs subtracted.
+# Returned system input/output signal names are those of Gsys.
+# Example: syssub(Gsys, Hsys) results in
 #
 #                  ________
 #             ----|  Gsys  |---
@@ -36,61 +38,78 @@
 #                  --------
 
 # Written by John Ingram July 1996
+# updated for variable numbers of input arguments by July 1999 A. S. Hodel
 
   save_val = implicit_str_to_num_ok;	# save for later
   implicit_str_to_num_ok = 1;
 
-  if(nargin != 2)
-    usage("syssub:  [sys] = syssub(Gsys,Hsys)");
-  endif
-
-  # check inputs
-  if(!is_struct(Gsys) | !is_struct(Hsys))
-    error("Both Gsys and Hsys must be a system data structure");
-  endif
-
-  # check for compatibility
-  [n,nz,mg,pg] = sysdimensions(Gsys);
-  [n,nz,mh,ph] = sysdimensions(Hsys);
-  if(mg != mh)
-    error(sprintf("Gsys inputs(%d) != Hsys inputs (%d)",mg,mh));
-  elseif(pg != ph)
-    error(sprintf("Gsys outputs(%d) != Hsys outputs (%d)",pg,ph));
-  endif
-
-  [Gst, Gin, Gout, Gyd] = sysgetsignals(Gsys);
-  [Hst, Hin, Hout, Hyd] = sysgetsignals(Hsys);
-
-  # check for digital to continuous addition
-  if (Gyd != Hyd)
-    error("can not add a discrete output to a continuous output");
+  if(nargin < 1)
+    usage("syssub: sys = syssub(Gsys{,Hsys,...})");
   endif
 
-  if( strcmp(sysgettype(Gsys),"tf") | strcmp(sysgettype(Hsys),"tf") )
-    # see if adding  transfer functions with identical denominators
-    [Gnum,Gden,GT,Gin,Gout] = sys2tf(Gsys);
-    [Hnum,Hden,HT,Hin,Hout] = sys2tf(Hsys);
-    if( (Hden == Gden) & (HT == GT) )
-      sys = tf2sys(Gnum-Hnum,Gden,GT,Gin,Gout);
-      return
+  # collect all arguments
+  arglist = list();
+  va_start();
+  for kk=1:nargin
+    arglist(kk) = va_arg();
+    if(!is_struct(nth(arglist,kk)))
+      error("syssub: argument %d is not a data structure",kk);
     endif
-    # if not, we go on and do the usual thing...
-  endif
+  endfor           
+
+  # check system dimensions
+  [n,nz,mg,pg,Gyd] = sysdimensions(nth(arglist,1));
+  for kk=2:nargin
+    [n,nz,mh,ph,Hyd] = sysdimensions(nth(arglist,kk));
+    if(mg != mh)
+      error("arg 1 has %d inputs; arg %d has vs %d inputs",mg,kk,mh);
+    elseif(pg != ph)
+      error("arg 1 has %d outputs; arg %d has vs %d outputs",pg,kk,ph);
+    elseif(norm(Gyd - Hyd))
+      warning("cannot add a discrete output to a continuous output");
+      error("Output type mismatch: arguments 1 and %d\n",kk);
+    endif
+  endfor
 
-  # make sure in ss form
-  Gsys = sysupdate(Gsys,"ss");
-  Hsys = sysupdate(Hsys,"ss");
-
-  # change signal names to avoid warning messages from sysgroup
-  Gsys = syssetsignals(Gsys,"in",sysdefioname(length(Gin),"Gin_u"));
-  Gsys = syssetsignals(Gsys,"out",sysdefioname(length(Gout),"Gout_u"));
-  Hsys = syssetsignals(Hsys,"in",sysdefioname(length(Hin),"Hin_u"));
-  Hsys = syssetsignals(Hsys,"out",sysdefioname(length(Hout),"Hout_u"));
+  # perform the subtract
+  if(nargin == 2)
+    Gsys = nth(arglist,1);   Hsys = nth(arglist,2);
+    if( strcmp(sysgettype(Gsys),"tf") | strcmp(sysgettype(Hsys),"tf") )
+      # see if subtracting  transfer functions with identical denominators
+      [Gnum,Gden,GT,Gin,Gout] = sys2tf(Gsys);
+      [Hnum,Hden,HT,Hin,Hout] = sys2tf(Hsys);
+      if(length(Hden) == length(Gden) )
+        if( (Hden == Gden) & (HT == GT) )
+          sys = tf2sys(Gnum+Hnum,Gden,GT,Gin,Gout);
+          return
+        endif
+        # if not, we go on and do the usual thing...
+      endif
+    endif
+  
+    # make sure in ss form
+    Gsys = sysupdate(Gsys,"ss");
+    Hsys = sysupdate(Hsys,"ss");
   
-  sys = sysgroup(Gsys,Hsys);
-
-  eyin = eye(mg); eyout = eye(pg);
-
-  sys = sysscale(sys,[eyout -eyout],[eyin;eyin],Gout,Gin);
-
+    # change signal names to avoid warning messages from sysgroup
+    Gsys = syssetsignals(Gsys,"in",sysdefioname(length(Gin),"Gin_u"));
+    Gsys = syssetsignals(Gsys,"out",sysdefioname(length(Gout),"Gout_u"));
+    Hsys = syssetsignals(Hsys,"in",sysdefioname(length(Hin),"Hin_u"));
+    Hsys = syssetsignals(Hsys,"out",sysdefioname(length(Hout),"Hout_u"));
+    
+    sys = sysgroup(Gsys,Hsys);
+  
+    eyin = eye(mg);
+    eyout = eye(pg);
+  
+    sys = sysscale(sys,[eyout -eyout],[eyin;eyin],Gout,Gin);
+  
+  else
+    # multiple systems (or a single system); combine together one by one
+    sys = nth(arglist,1);
+    for kk=2:length(arglist)
+      sys = syssub(sys,nth(arglist,kk));
+    endfor
+  endif
+  
 endfunction
diff --git a/scripts/control/sysupdate.m b/scripts/control/sysupdate.m
--- a/scripts/control/sysupdate.m
+++ b/scripts/control/sysupdate.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tf2ss.m b/scripts/control/tf2ss.m
--- a/scripts/control/tf2ss.m
+++ b/scripts/control/tf2ss.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tf2sys.m b/scripts/control/tf2sys.m
--- a/scripts/control/tf2sys.m
+++ b/scripts/control/tf2sys.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tf2sysl.m b/scripts/control/tf2sysl.m
--- a/scripts/control/tf2sysl.m
+++ b/scripts/control/tf2sysl.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tf2zp.m b/scripts/control/tf2zp.m
--- a/scripts/control/tf2zp.m
+++ b/scripts/control/tf2zp.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tfout.m b/scripts/control/tfout.m
--- a/scripts/control/tfout.m
+++ b/scripts/control/tfout.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tzero.m b/scripts/control/tzero.m
--- a/scripts/control/tzero.m
+++ b/scripts/control/tzero.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/tzero2.m b/scripts/control/tzero2.m
--- a/scripts/control/tzero2.m
+++ b/scripts/control/tzero2.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1993 John W. Eaton
+# Copyright (C) 1993 Auburn University.  All Rights Reserved
 # 
 # This file is part of Octave.
 # 
@@ -41,19 +41,19 @@
       fprintf (stderr, "tzero: number of inputs,outputs differ.  squaring up");
       if (p > m)
 	fprintf (stderr, "       by padding b and d with zeros.");
-	b = [b, zeros (n, p-m)];
-	d = [d, zeros (p, p-m)];
+	b = [b, (zeros (n, p-m))];
+	d = [d, (zeros (p, p-m))];
 	m = p;
       else
 	fprintf (stderr, "       by padding c and d with zeros.");
-	c = [c; zeros (m-p, n)];
-	d = [d; zeros (m-p, m)];
+	c = [c; (zeros (m-p, n))];
+	d = [d; (zeros (m-p, m))];
 	p = m;
       endif
       fprintf (stderr, "This is a kludge.  Try again with SISO system.");
     endif
     ab = [-a, -b; c, d];
-    bb = [eye (n), zeros (n, m); zeros (p, n), zeros (p, m)];
+    bb = [(eye (n)), (zeros (n, m)); (zeros (p, n)), (zeros (p, m))];
     [ab,bb] = balance (ab, bb);
     zr = -qz (ab, bb);
   else
diff --git a/scripts/control/unpacksys.m b/scripts/control/unpacksys.m
--- a/scripts/control/unpacksys.m
+++ b/scripts/control/unpacksys.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgfmul.m b/scripts/control/zgfmul.m
--- a/scripts/control/zgfmul.m
+++ b/scripts/control/zgfmul.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgfslv.m b/scripts/control/zgfslv.m
--- a/scripts/control/zgfslv.m
+++ b/scripts/control/zgfslv.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zginit.m b/scripts/control/zginit.m
--- a/scripts/control/zginit.m
+++ b/scripts/control/zginit.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgpbal.m b/scripts/control/zgpbal.m
--- a/scripts/control/zgpbal.m
+++ b/scripts/control/zgpbal.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgreduce.m b/scripts/control/zgreduce.m
--- a/scripts/control/zgreduce.m
+++ b/scripts/control/zgreduce.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgrownorm.m b/scripts/control/zgrownorm.m
--- a/scripts/control/zgrownorm.m
+++ b/scripts/control/zgrownorm.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgscal.m b/scripts/control/zgscal.m
--- a/scripts/control/zgscal.m
+++ b/scripts/control/zgscal.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgsgiv.m b/scripts/control/zgsgiv.m
--- a/scripts/control/zgsgiv.m
+++ b/scripts/control/zgsgiv.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zgshsr.m b/scripts/control/zgshsr.m
--- a/scripts/control/zgshsr.m
+++ b/scripts/control/zgshsr.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zp2ss.m b/scripts/control/zp2ss.m
--- a/scripts/control/zp2ss.m
+++ b/scripts/control/zp2ss.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zp2ssg2.m b/scripts/control/zp2ssg2.m
--- a/scripts/control/zp2ssg2.m
+++ b/scripts/control/zp2ssg2.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zp2sys.m b/scripts/control/zp2sys.m
--- a/scripts/control/zp2sys.m
+++ b/scripts/control/zp2sys.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
@@ -41,12 +41,16 @@
   if( ! (is_vector(zer) | isempty(zer) ) )
     error("zer must be a vector or empty");
   endif
-  zer = reshape(zer,1,length(zer));		# make it a row vector
+  if(!isempty(zer))
+    zer = reshape(zer,1,length(zer));		# make it a row vector
+  endif
 
   if( ! (is_vector(pol) | isempty(pol)))
     error("pol must be a vector");
   endif
-  pol = reshape(pol,1,length(pol));
+  if(!isempty(pol))
+    pol = reshape(pol,1,length(pol));
+  endif
 
   if (! is_scalar(k))
      error('k must be a scalar');
diff --git a/scripts/control/zp2tf.m b/scripts/control/zp2tf.m
--- a/scripts/control/zp2tf.m
+++ b/scripts/control/zp2tf.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996,1998 A. Scottedward Hodel 
+# Copyright (C) 1996,1998 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #
diff --git a/scripts/control/zpout.m b/scripts/control/zpout.m
--- a/scripts/control/zpout.m
+++ b/scripts/control/zpout.m
@@ -1,4 +1,4 @@
-# Copyright (C) 1996 A. Scottedward Hodel 
+# Copyright (C) 1996 Auburn University.  All Rights Reserved
 #
 # This file is part of Octave. 
 #