--- /dev/null
+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;
+