--- /dev/null
+## Copyright (C) 2009, 2012 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 -*-
+## Set or modify properties of TF objects.
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2009
+## Version: 0.2
+
+function sys = __set__ (sys, prop, val)
+
+ switch (prop) # {<internal name>, <user name>}
+ case "num"
+ num = __vec2tfpoly__ (val);
+ __tf_dim__ (num, sys.den);
+ sys.num = num;
+
+ case "den"
+ den = __vec2tfpoly__ (val);
+ __tf_dim__ (sys.num, den);
+ sys.den = den;
+
+ case {"tfvar", "variable"}
+ if (ischar (val))
+ sys.tfvar = val;
+ else
+ error ("tf: set: invalid transfer function variable");
+ endif
+
+ case "inv"
+ if (! isdt (sys))
+ error ("tf: set: property 'inv' requires discrete-time system");
+ elseif (! isscalar (val))
+ error ("tf: set: property 'inv' must be a scalar logical");
+ else
+ sys.inv = logical (val);
+ endif
+
+ otherwise
+ error ("tf: set: invalid property name");
+
+ endswitch
+
+endfunction