--- /dev/null
+## Copyright (C) 2009, 2010, 2011, 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 -*-
+## Frequency response of SS models.
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2009
+## Version: 0.5
+
+function H = __freqresp__ (sys, w, resptype = 0, cellflag = false)
+
+ if (sys.scaled == false)
+ sys = prescale (sys);
+ endif
+
+ [a, b, c, d, e, tsam] = dssdata (sys);
+
+ if (resptype != 0 && columns (b) != rows (c))
+ error ("ss: freqresp: system must be square for response type %d", resptype);
+ endif
+
+ if (isct (sys)) # continuous system
+ s = i * w;
+ else # discrete system
+ s = exp (i * w * abs (tsam));
+ endif
+
+ switch (resptype)
+ case 0 # default system
+ H = arrayfun (@(x) c/(x*e - a)*b + d, s, "uniformoutput", false);
+
+ case 1 # inversed system
+ H = arrayfun (@(x) inv (c/(x*e - a)*b + d), s, "uniformoutput", false);
+
+ case 2 # inversed sensitivity
+ j = eye (columns (b));
+ H = arrayfun (@(x) j + c/(x*e - a)*b + d, s, "uniformoutput", false);
+
+ case 3 # inversed complementary sensitivity
+ j = eye (columns (b));
+ H = arrayfun (@(x) j + inv (c/(x*e - a)*b + d), s, "uniformoutput", false);
+
+ otherwise
+ error ("ss: freqresp: invalid response type");
+ endswitch
+
+ if (! cellflag)
+ H = cat (3, H{:});
+ endif
+
+endfunction
\ No newline at end of file