--- /dev/null
+function s = Urrextrapolation(X)
+
+% s = Urrextrapolation(X)
+% RRE vector extrapolation see
+% Smith, Ford & Sidi SIREV 29 II 06/1987
+
+% This file is part of
+%
+% SECS2D - A 2-D Drift--Diffusion Semiconductor Device Simulator
+% -------------------------------------------------------------------
+% Copyright (C) 2004-2006 Carlo de Falco
+%
+%
+%
+% SECS2D 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 2 of the License, or
+% (at your option) any later version.
+%
+% SECS2D 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 SECS2D; If not, see <http://www.gnu.org/licenses/>.
+
+ if (Ucolumns(X)>Urows(X))
+ X=X';
+ end
+
+ % compute first and second variations
+ U = X(:,2:end) - X(:,1:end-1);
+ V = U(:,2:end) - U(:,1:end-1);
+
+ % eliminate unused u_k column
+ U(:,end) = [];
+
+ s = X(:,1) - U * pinv(V) * U(:,1);
+