/usr/share/octave/packages/tsa-4.2.7/ucp.m is in octave-tsa 4.2.7-1build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | 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 11693 2013-03-04 06:40:14Z 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;
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