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+## Copyright (C) 1996 Auburn University.  All rights reserved.
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by the
+## Free Software Foundation; either version 2, or (at your option) any
+## later version.
+##
+## Octave is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+## for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, write to the Free
+## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
+
+## -*- texinfo -*-
+##@deftypefn {Function File} {@var{outputs} =} rldemo (@var{inputs})
+##Octave Controls toolbox demo: Root Locus demo
+##@end deftypefn
+
+## Author: David Clem
+## Created: August 15, 1994
+## Updated by John Ingram December 1996
+
+function rldemo ()
+
+  while (1)
+    clc
+    k = menu("Octave Root Locus Demo", ...
+        "Display continuous system's open loop poles and zeros (pzmap)", ...
+        "Display discrete system's open loop poles and zeros (pzmap)", ...
+        "Display root locus diagram of SISO continuous system (rlocus)", ...
+        "Display root locus diagram of SISO discrete system (rlocus)", ...
+        "Return to main demo menu");
+    gset autoscale
+    if (k == 1)
+      clc
+      help pzmap
+      prompt
+
+      clc
+      disp("Display continuous system's open loop poles and zeros (pzmap)\n");
+      disp("Example #1, Consider the following continuous transfer function:");
+      cmd = "sys1 = tf2sys([1.5, 18.5, 6], [1, 4, 155, 302, 5050]);";
+      disp(cmd);
+      eval(cmd);
+      cmd ="sysout(sys1);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys1,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("View the system's open loop poles and zeros with the command:")
+      cmd = "pzmap(sys1);";
+      run_cmd
+      prompt
+
+      clc
+      disp("Example #2, Consider the following set of poles and zeros:");
+      cmd = "sys2 = zp2sys([-1, 5, -23],[-1, -10, -7+5i, -7-5i],5);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys2);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nThe pzmap command for the zp form is the same as the tf form:")
+      cmd = "pzmap(sys2);";
+      run_cmd;
+      disp("\nThe internal representation of the system is not important;");
+      disp("pzmap automatically sorts it out internally.");
+      prompt;
+
+      clc
+      disp("Example #3, Consider the following state space system:\n");
+      cmd = "sys3=ss2sys([0, 1; -10, -11], [0; 1], [0, -2], 1);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys3);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys3,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("\nOnce again, the pzmap command is the same:");
+      cmd = "pzmap(sys3);";
+      run_cmd;
+      prompt;
+
+      closeplot
+      clc
+
+    elseif (k == 2)
+      clc
+      help pzmap
+      prompt
+
+      clc
+      disp("\nDisplay discrete system's open loop poles and zeros (pzmap)\n");
+      disp("First we must define a sampling time, as follows:\n");
+      cmd = "Tsam = 1;";
+      run_cmd;
+      disp("Example #1, Consider the following discrete transfer function:");
+      cmd = "sys1 = tf2sys([1.05, -0.09048], [1, -2, 1],Tsam);";
+      disp(cmd);
+      eval(cmd);
+      cmd ="sysout(sys1);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys1,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("View the system's open loop poles and zeros with the command:")
+      cmd = "pzmap(sys1);";
+      run_cmd
+      prompt
+
+      clc
+      disp("Example #2, Consider the following set of discrete poles and zeros:");
+      cmd = "sys2 = zp2sys(-0.717, [1, -0.368], 3.68, Tsam);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys2);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nThe pzmap command for the zp form is the same as the tf form:")
+      cmd = "pzmap(sys2);";
+      run_cmd;
+      disp("\nThe internal representation of the system is not important;");
+      disp("pzmap automatically sorts it out internally.");
+      prompt;
+
+      clc
+      disp("Example #3, Consider the following discrete state space system:\n");
+      cmd = "sys3=ss2sys([1, 0.0952; 0, 0.905], [0.00484; 0.0952], [1, 0], 0, Tsam);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys3);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys3,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("\nOnce again, the pzmap command is the same:");
+      cmd = "pzmap(sys3);";
+      run_cmd;
+      prompt;
+
+      closeplot
+      clc
+
+    elseif (k == 3)
+      clc
+      help rlocus
+      prompt;
+
+      clc
+      disp("Display root locus of a continuous SISO system (rlocus)\n")
+      disp("Example #1, Consider the following continuous transfer function:");
+      cmd = "sys1 = tf2sys([1.5, 18.5, 6],[1, 4, 155, 302, 5050]);";
+      disp(cmd);
+      eval(cmd);
+      cmd ="sysout(sys1);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys1,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("\nWhen using rlocus, inital system poles are displayed as X's.")
+      disp("Moving poles are displayed as diamonds.  Zeros are displayed as")
+      disp("boxes.  The simplest form of the rlocus command is as follows:")
+      cmd = "rlocus(sys1);";
+      run_cmd
+      disp("\nrlocus automatically selects the minimum and maximum gains based")
+      disp("on the real-axis locus breakpoints.  The plot limits are chosen")
+      disp("to be no more than 10 times the maximum magnitude of the open")
+      disp("loop poles/zeros.");
+      prompt
+
+      clc
+      disp("Example #2, Consider the following set of poles and zeros:");
+      cmd = "sys2 = zp2sys([],[0, -20, -2, -0.1],5);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys2);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nThe rlocus command for the zp form is the same as the tf form:")
+      cmd = "rlocus(sys2);";
+      run_cmd;
+      disp("\nThe internal representation of the system is not important;");
+      disp("rlocus automatically sorts it out internally.");
+      prompt;
+
+      clc
+      disp("Example #3, Consider the following state space system:\n");
+      cmd = "sys3=ss2sys([0, 1; -10, -11], [0; 1], [0, -2], 0);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys3);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys3,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("\nOnce again, the rlocus command is the same:");
+      cmd = "rlocus(sys3);";
+      run_cmd;
+
+      disp("\nNo matter what form the system is in, the rlocus command works the");
+      disp("the same.");
+      prompt;
+
+      closeplot
+      clc
+
+    elseif (k == 4)
+      clc
+      help rlocus
+      prompt
+
+      clc
+      disp("Display root locus of a discrete SISO system (rlocus)\n")
+      disp("First we must define a sampling time, as follows:\n");
+      cmd = "Tsam = 1;";
+      run_cmd;
+      disp("Example #1, Consider the following discrete transfer function:");
+      cmd = "sys1 = tf2sys([1.05, -0.09048],[1, -2, 1],Tsam);";
+      disp(cmd);
+      eval(cmd);
+      cmd ="sysout(sys1);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys1,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("\nWhen using rlocus, inital system poles are displayed as X's.")
+      disp("Moving poles are displayed as diamonds.  Zeros are displayed as")
+      disp("boxes.  The simplest form of the rlocus command is as follows:")
+      cmd = "rlocus(sys1);";
+      run_cmd
+      disp("\nrlocus automatically selects the minimum and maximum gains based")
+      disp("on the real-axis locus breakpoints.  The plot limits are chosen")
+      disp("to be no more than 10 times the maximum magnitude of the open")
+      disp("loop poles/zeros.");
+      prompt
+
+      clc
+      disp("Example #2, Consider the following set of discrete poles and zeros:");
+      cmd = "sys2 = zp2sys(-0.717, [1, -0.368], 3.68, Tsam);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys2);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nThe rlocus command for the zp form is the same as the tf form:")
+      cmd = "rlocus(sys2);";
+      run_cmd;
+      disp("\nThe internal representation of the system is not important;");
+      disp("rlocus automatically sorts it out internally.  Also, it does not");
+      disp("matter if the system is continuous or discrete.  rlocus also sorts");
+      disp("this out automatically");
+      prompt;
+
+      clc
+      disp("Example #3, Consider the following discrete state space system:\n");
+      cmd = "sys3=ss2sys([1, 0.0952; 0, 0.905], [0.00484; 0.0952], [1, 0], 0, Tsam);";
+      disp(cmd);
+      eval(cmd);
+      cmd = "sysout(sys3);";
+      disp(cmd);
+      eval(cmd);
+      disp("\nPole-zero form can be obtained as follows:");
+      cmd = "sysout(sys3,""zp"");";
+      disp(cmd);
+      eval(cmd);
+      disp("\nOnce again, the rlocus command is the same:");
+      cmd = "rlocus(sys3);";
+      run_cmd;
+
+      disp("\nNo matter what form the system is in, the rlocus command works the");
+      disp("the same.");
+
+      prompt;
+
+      closeplot
+      clc
+
+    elseif (k == 5)
+      return
+    endif
+  endwhile
+endfunction