Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / @lti / dssdata.m

diff --git a/octave_packages/control-2.3.52/@lti/dssdata.m b/octave_packages/control-2.3.52/@lti/dssdata.m
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+## Copyright (C) 2010, 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 -*-
+## @deftypefn {Function File} {[@var{a}, @var{b}, @var{c}, @var{d}, @var{e}, @var{tsam}] =} dssdata (@var{sys})
+## @deftypefnx {Function File} {[@var{a}, @var{b}, @var{c}, @var{d}, @var{e}, @var{tsam}] =} dssdata (@var{sys}, @var{[]})
+## Access descriptor state-space model data.
+## Argument @var{sys} is not limited to descriptor state-space models.
+## If @var{sys} is not a descriptor state-space model, it is converted automatically.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## Any type of LTI model.
+## @item []
+## In case @var{sys} is not a dss model (descriptor matrix @var{e} empty),
+## @code{dssdata (sys, [])} returns the empty element @code{e = []} whereas
+## @code{dssdata (sys)} returns the identity matrix @code{e = eye (size (a))}.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item a
+## State transition matrix (n-by-n).
+## @item b
+## Input matrix (n-by-m).
+## @item c
+## Measurement matrix (p-by-n).
+## @item d
+## Feedthrough matrix (p-by-m).
+## @item e
+## Descriptor matrix (n-by-n).
+## @item tsam
+## Sampling time in seconds.  If @var{sys} is a continuous-time model,
+## a zero is returned.
+## @end table
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: September 2010
+## Version: 0.2
+
+function [a, b, c, d, e, tsam, scaled] = dssdata (sys, flg = 0)
+
+  ## NOTE: In case sys is not a dss model (matrice e empty),
+  ##       dssdata (sys, []) returns e = [] whereas
+  ##       dssdata (sys) returns e = eye (size (a))
+
+  if (nargin > 2)
+    print_usage ();
+  endif
+
+  if (! isa (sys, "ss"))
+    sys = ss (sys);
+  endif
+
+  [a, b, c, d, e, ~, scaled] = __sys_data__ (sys);
+
+  if (isempty (e) && ! isempty (flg))
+    e = eye (size (a));  # return eye for ss models
+  endif
+
+  tsam = sys.tsam;
+
+endfunction
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