Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / tsa-4.2.4 / ucp.m

diff --git a/octave_packages/tsa-4.2.4/ucp.m b/octave_packages/tsa-4.2.4/ucp.m
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+function b=ucp(c)
+% UCP(C) tests if the polynomial C is a Unit-Circle-Polynomial.
+%      It tests if all roots lie inside the unit circle like
+%       B=ucp(C) does the same as
+%      B=all(abs(roots(C))<1) but much faster.
+%      The Algorithm is based on the Jury-Scheme.
+%      C are the elements of the Polynomial
+%      C(1)*X^N + ... + C(N)*X + C(N+1).
+% 
+% REFERENCES:
+%  O. Foellinger "Lineare Abtastsysteme", Oldenburg Verlag, Muenchen, 1986.
+%  F. Gausch "Systemtechnik", Textbook, University of Technology Graz, 1993. 
+
+
+%      $Id: ucp.m 5090 2008-06-05 08:12:04Z schloegl $
+%      Copyright (C) 1996-1999,2008 by Alois Schloegl <a.schloegl@ieee.org>
+%
+%    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/>.
+
+[lr,lc] = size(c);
+
+% JURY-Scheme
+b=ones(lr,1);
+lambda=zeros(lr,1);
+while (lc > 1), 
+       lambda = c(:,lc)./c(:,1);
+%       disp([lc,size(lambda), sum(b),toc]);
+       % ratio must be less then 1
+       b = b & (abs(lambda) < 1);
+       % and reduced polynomial must be a UCP, too.
+       c(:,1:lc-1) = c(:,1:lc-1) - lambda(:,ones(1,lc-1)).*c(:,lc:-1:2);
+       lc = lc-1;
+end;
+