--- /dev/null
+## Copyright (C) 2009, 2011 Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope 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.
+##
+## LTI Syncope 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 LTI Syncope. If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## Horizontal concatenation of LTI objects. If necessary, object conversion
+## is done by sys_group. Used by Octave for "[sys1, sys2]".
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: September 2009
+## Version: 0.2
+
+function sys = horzcat (sys, varargin)
+
+ for k = 1 : (nargin-1)
+
+ sys1 = sys;
+ sys2 = varargin{k};
+
+ [p1, m1] = size (sys1);
+ [p2, m2] = size (sys2);
+
+ if (p1 != p2)
+ error ("lti: horzcat: number of system outputs incompatible: [(%dx%d), (%dx%d)]",
+ p1, m1, p2, m2);
+ endif
+
+ sys = __sys_group__ (sys1, sys2);
+
+ out_scl = [eye(p1), eye(p2)];
+
+ sys = out_scl * sys;
+
+ endfor
+
+endfunction
+
+
+## Rowwise concatenation of two systems in state-space form
+## Test from SLICOT AB05OD
+%!shared M, Me
+%! A1 = [ 1.0 0.0 -1.0
+%! 0.0 -1.0 1.0
+%! 1.0 1.0 2.0 ];
+%!
+%! B1 = [ 1.0 1.0 0.0
+%! 2.0 0.0 1.0 ].';
+%!
+%! C1 = [ 3.0 -2.0 1.0
+%! 0.0 1.0 0.0 ];
+%!
+%! D1 = [ 1.0 0.0
+%! 0.0 1.0 ];
+%!
+%! A2 = [-3.0 0.0 0.0
+%! 1.0 0.0 1.0
+%! 0.0 -1.0 2.0 ];
+%!
+%! B2 = [ 0.0 -1.0 0.0
+%! 1.0 0.0 2.0 ].';
+%!
+%! C2 = [ 1.0 1.0 0.0
+%! 1.0 1.0 -1.0 ];
+%!
+%! D2 = [ 1.0 1.0
+%! 0.0 1.0 ];
+%!
+%! sys1 = ss (A1, B1, C1, D1);
+%! sys2 = ss (A2, B2, C2, D2);
+%! sys = [sys1, sys2];
+%! [A, B, C, D] = ssdata (sys);
+%! M = [A, B; C, D];
+%!
+%! Ae = [ 1.0000 0.0000 -1.0000 0.0000 0.0000 0.0000
+%! 0.0000 -1.0000 1.0000 0.0000 0.0000 0.0000
+%! 1.0000 1.0000 2.0000 0.0000 0.0000 0.0000
+%! 0.0000 0.0000 0.0000 -3.0000 0.0000 0.0000
+%! 0.0000 0.0000 0.0000 1.0000 0.0000 1.0000
+%! 0.0000 0.0000 0.0000 0.0000 -1.0000 2.0000 ];
+%!
+%! Be = [ 1.0000 2.0000 0.0000 0.0000
+%! 1.0000 0.0000 0.0000 0.0000
+%! 0.0000 1.0000 0.0000 0.0000
+%! 0.0000 0.0000 0.0000 1.0000
+%! 0.0000 0.0000 -1.0000 0.0000
+%! 0.0000 0.0000 0.0000 2.0000 ];
+%!
+%! Ce = [ 3.0000 -2.0000 1.0000 1.0000 1.0000 0.0000
+%! 0.0000 1.0000 0.0000 1.0000 1.0000 -1.0000 ];
+%!
+%! De = [ 1.0000 0.0000 1.0000 1.0000
+%! 0.0000 1.0000 0.0000 1.0000 ];
+%!
+%! Me = [Ae, Be; Ce, De];
+%!
+%!assert (M, Me, 1e-4);