Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / polystab.m

diff --git a/octave_packages/signal-1.1.3/polystab.m b/octave_packages/signal-1.1.3/polystab.m
new file mode 100644 (file)
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+++ b/octave_packages/signal-1.1.3/polystab.m
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+## Copyright (C) 2001 Paul Kienzle <pkienzle@users.sf.net>
+##
+## This program 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.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## b = polystab(a)
+##
+## Stabalize the polynomial transfer function by replacing all roots
+## outside the unit circle with their reflection inside the unit circle.
+
+function b = polystab(a)
+
+   r = roots(a);
+   v = find(abs(r)>1);
+   r(v) = 1./conj(r(v));
+   b = a(1) * poly ( r );
+   if isreal(a), b = real(b); endif
+
+endfunction