--- /dev/null
+## Copyright (C) 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 -*-
+## Conjugate transpose or pertransposition of LTI objects.
+## Used by Octave for "sys'".
+## For a transfer-function matrix G, G' denotes the conjugate
+## of G given by G.'(-s) for a continuous-time system or G.'(1/z)
+## for a discrete-time system.
+## The frequency response of the pertransposition of G is the
+## Hermitian (conjugate) transpose of G(jw), i.e.
+## freqresp (G', w) = freqresp (G, w)'.
+## @strong{WARNING:} Do @strong{NOT} use this for dual problems,
+## use the transpose "sys.'" (note the dot) instead.
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: May 2012
+## Version: 0.1
+
+function sys = ctranspose (sys)
+
+ if (nargin != 1) # prevent sys = ctranspose (sys1, sys2, sys3, ...)
+ error ("lti: ctranspose: this is an unary operator");
+ endif
+
+ [p, m] = size (sys);
+ ct = isct (sys);
+
+ sys = __ctranspose__ (sys, ct);
+
+ sys.inname = repmat ({""}, p, 1);
+ sys.outname = repmat ({""}, m, 1);
+
+endfunction
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