--- /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 -*-
+## @deftypefn {Function File} {@var{s} =} tf (@var{"s"})
+## @deftypefnx {Function File} {@var{z} =} tf (@var{"z"}, @var{tsam})
+## @deftypefnx {Function File} {@var{sys} =} tf (@var{sys})
+## @deftypefnx {Function File} {@var{sys} =} tf (@var{num}, @var{den}, @dots{})
+## @deftypefnx {Function File} {@var{sys} =} tf (@var{num}, @var{den}, @var{tsam}, @dots{})
+## Create or convert to transfer function model.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## LTI model to be converted to transfer function.
+## @item num
+## Numerator or cell of numerators. Each numerator must be a row vector
+## containing the coefficients of the polynomial in descending powers of
+## the transfer function variable.
+## num@{i,j@} contains the numerator polynomial from input j to output i.
+## In the SISO case, a single vector is accepted as well.
+## @item den
+## Denominator or cell of denominators. Each denominator must be a row vector
+## containing the coefficients of the polynomial in descending powers of
+## the transfer function variable.
+## den@{i,j@} contains the denominator polynomial from input j to output i.
+## In the SISO case, a single vector is accepted as well.
+## @item tsam
+## Sampling time in seconds. If @var{tsam} is not specified, a continuous-time
+## model is assumed.
+## @item @dots{}
+## Optional pairs of properties and values.
+## Type @command{set (tf)} for more information.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item sys
+## Transfer function model.
+## @end table
+##
+## @strong{Example}
+## @example
+## @group
+## octave:1> s = tf ("s");
+## octave:2> G = 1/(s+1)
+##
+## Transfer function "G" from input "u1" to output ...
+##
+## 1
+## y1: -----
+## s + 1
+##
+## Continuous-time model.
+## @end group
+## @end example
+## @example
+## @group
+## octave:3> z = tf ("z", 0.2);
+## octave:4> H = 0.095/(z-0.9)
+##
+## Transfer function "H" from input "u1" to output ...
+##
+## 0.095
+## y1: -------
+## z - 0.9
+##
+## Sampling time: 0.2 s
+## Discrete-time model.
+## @end group
+## @end example
+## @example
+## @group
+## octave:5> num = @{[1, 5, 7], [1]; [1, 7], [1, 5, 5]@};
+## octave:6> den = @{[1, 5, 6], [1, 2]; [1, 8, 6], [1, 3, 2]@};
+## octave:7> sys = tf (num, den)
+##
+## Transfer function "sys" from input "u1" to output ...
+##
+## s^2 + 5 s + 7
+## y1: -------------
+## s^2 + 5 s + 6
+##
+## s + 7
+## y2: -------------
+## s^2 + 8 s + 6
+##
+## Transfer function "sys" from input "u2" to output ...
+##
+## 1
+## y1: -----
+## s + 2
+##
+## s^2 + 5 s + 5
+## y2: -------------
+## s^2 + 3 s + 2
+##
+## Continuous-time model.
+## octave:8>
+## @end group
+## @end example
+##
+## @seealso{ss, dss}
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: September 2009
+## Version: 0.3
+
+function sys = tf (num = {}, den = {}, varargin)
+
+ ## model precedence: frd > ss > zpk > tf > double
+ ## inferiorto ("frd", "ss", "zpk"); # error if de-commented. bug in octave?
+ superiorto ("double");
+
+ argc = 0; # initialize argument count
+
+ switch (nargin)
+ case 0 # sys = tf ()
+ tsam = -2; # undefined sampling time
+ tfvar = "x"; # undefined transfer function variable
+
+ case 1
+ if (isa (num, "tf")) # already in tf form sys = tf (tfsys)
+ sys = num;
+ return;
+ elseif (isa (num, "lti")) # another lti object sys = tf (sys)
+ [sys, numlti] = __sys2tf__ (num);
+ sys.lti = numlti; # preserve lti properties
+ return;
+ elseif (is_real_matrix (num)) # static gain sys = tf (4), sys = tf (matrix)
+ num = num2cell (num);
+ num = __vec2tfpoly__ (num);
+ [p, m] = size (num);
+ den = tfpolyones (p, m); # denominators are all 1
+ tsam = -2; # undefined sampling time
+ tfvar = "x"; # undefined transfer function variable
+ elseif (ischar (num)) # s = tf ("s")
+ tfvar = num;
+ num = __vec2tfpoly__ ([1, 0]);
+ den = __vec2tfpoly__ ([1]);
+ tsam = 0;
+ else
+ print_usage ();
+ endif
+
+ case 2
+ if (ischar (num) && issample (den, -1)) # z = tf ("z", 0.3)
+ tfvar = num;
+ tsam = den;
+ num = __vec2tfpoly__ ([1, 0]);
+ den = __vec2tfpoly__ ([1]);
+ else # sys = tf (num, den)
+ num = __vec2tfpoly__ (num);
+ den = __vec2tfpoly__ (den);
+ tfvar = "s";
+ tsam = 0;
+ endif
+
+ otherwise # default case sys = tf (num, den, ...)
+ num = __vec2tfpoly__ (num);
+ den = __vec2tfpoly__ (den);
+ argc = numel (varargin); # number of additional arguments after num and den
+ if (issample (varargin{1}, -10)) # sys = tf (num, den, tsam, "prop1", val1, ...)
+ tsam = varargin{1}; # sampling time, could be 0 as well
+ argc--; # tsam is not a property-value pair
+ if (tsam == 0)
+ tfvar = "s";
+ else
+ tfvar = "z";
+ endif
+ if (argc > 0) # if there are any properties and values ...
+ varargin = varargin(2:end); # remove tsam from property-value list
+ endif
+ else # sys = tf (num, den, "prop1", val1, ...)
+ tsam = 0; # continuous-time
+ tfvar = "s";
+ endif
+ endswitch
+
+ [p, m] = __tf_dim__ (num, den); # determine number of outputs and inputs
+
+ tfdata = struct ("num", {num},
+ "den", {den},
+ "tfvar", tfvar,
+ "inv", false); # struct for tf-specific data
+
+ ltisys = lti (p, m, tsam); # parent class for general lti data
+
+ sys = class (tfdata, "tf", ltisys); # create tf object
+
+ if (argc > 0) # if there are any properties and values, ...
+ sys = set (sys, varargin{:}); # use the general set function
+ endif
+
+endfunction
+
git://git.creatis.insa-lyon.fr / CreaPhase.git / blobdiff