Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / @ss / __freqresp__.m

diff --git a/octave_packages/control-2.3.52/@ss/__freqresp__.m b/octave_packages/control-2.3.52/@ss/__freqresp__.m
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+## 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
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