Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / @lti / isstable.m

diff --git a/octave_packages/control-2.3.52/@lti/isstable.m b/octave_packages/control-2.3.52/@lti/isstable.m
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+++ b/octave_packages/control-2.3.52/@lti/isstable.m
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+## Copyright (C) 2009, 2010   Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope 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 3 of the License, or
+## (at your option) any later version.
+##
+## LTI Syncope 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 LTI Syncope.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{bool} =} isstable (@var{sys})
+## @deftypefnx {Function File} {@var{bool} =} isstable (@var{sys}, @var{tol})
+## Determine whether LTI system is stable.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## LTI system.
+## @item tol
+## Optional tolerance for stability.  Default value is 0.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item bool = 0
+## System is not stable.
+## @item bool = 1
+## System is stable.
+## @end table
+##
+## @example
+## @group
+##   real (p) < -tol*(1 + abs (p))    continuous-time
+##   abs (p) < 1 - tol                discrete-time
+## @end group
+## @end example
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2009
+## Version: 0.2
+
+function bool = isstable (sys, tol = 0)
+
+  if (nargin > 2)
+    print_usage ();
+  endif
+
+  pol = pole (sys);
+  ct = isct (sys);
+
+  bool = __is_stable__ (pol, ct, tol);
+
+endfunction