Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / @ss / __pole__.m

diff --git a/octave_packages/control-2.3.52/@ss/__pole__.m b/octave_packages/control-2.3.52/@ss/__pole__.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 -*-
+## Poles of SS object.
+
+## Special thanks to Peter Benner for his advice.
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2009
+## Version: 0.3
+
+function pol = __pole__ (sys)
+
+  if (isempty (sys.e))
+    pol = eig (sys.a);
+  else
+    pol = eig (sys.a, sys.e);
+    tol = norm ([sys.a, sys.e], 2);
+    idx = find (abs (pol) < tol/eps);
+    pol = pol(idx);
+  endif
+
+endfunction
+
+
+## sys = ss (-2, 3, 4, 0)
+## sysi = inv (sys)  # singular e
+## p = pole (sysi)
+## infinite poles correct?
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