Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / filt.m

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+## 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 -*-
+## @deftypefn {Function File} {@var{sys} =} filt (@var{num}, @var{den}, @dots{})
+## @deftypefnx {Function File} {@var{sys} =} filt (@var{num}, @var{den}, @var{tsam}, @dots{})
+## Create discrete-time transfer function model from data in DSP format.
+##
+## @strong{Inputs}
+## @table @var
+## @item num
+## Numerator or cell of numerators.  Each numerator must be a row vector
+## containing the coefficients of the polynomial in ascending powers of z^-1.
+## 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 ascending powers of z^-1.
+## 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,
+## default value -1 (unspecified) is taken.
+## @item @dots{}
+## Optional pairs of properties and values.
+## Type @command{set (filt)} for more information.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item sys
+## Discrete-time transfer function model.
+## @end table
+##
+## @strong{Example}
+## @example
+## @group
+##                 3 z^-1     
+## H(z^-1) = -------------------
+##           1 + 4 z^-1 + 2 z^-2
+##
+## octave:1> H = filt ([0, 3], [1, 4, 2])
+## 
+## Transfer function 'H' from input 'u1' to output ...
+## 
+##             3 z^-1       
+##  y1:  -------------------
+##       1 + 4 z^-1 + 2 z^-2
+## 
+## Sampling time: unspecified
+## Discrete-time model.
+## @end group
+## @end example
+##
+## @seealso{tf}
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: April 2012
+## Version: 0.1
+
+function sys = filt (num = {}, den = {}, tsam = -1, varargin)
+
+  switch (nargin)
+    case 0              # filt ()
+      sys = tf ();
+      ## sys.inv = true;
+      return;
+
+    case 1              # filt (sys), filt (matrix)
+      if (isa (num, "lti") || is_real_matrix (num))
+        sys = tf (num);
+        ## sys.inv = true;  # would be a problem for continuous-time LTI models
+        return;
+      else
+        print_usage ();
+      endif
+
+    otherwise           # filt (num, den, ...)
+      if (! iscell (num))
+        num = {num};
+      endif
+      if (! iscell (den))
+        den = {den};
+      endif
+
+      ## convert from z^-1 to z
+      ## expand each channel by z^x, where x is the largest exponent of z^-1 (z^-x)
+
+      ## remove trailing zeros
+      ## such that polynomials are as short as possible
+      num = cellfun (@__remove_trailing_zeros__, num, "uniformoutput", false);
+      den = cellfun (@__remove_trailing_zeros__, den, "uniformoutput", false);
+
+      ## make numerator and denominator polynomials equally long
+      ## by adding trailing zeros
+      lnum = cellfun (@length, num, "uniformoutput", false);
+      lden = cellfun (@length, den, "uniformoutput", false);
+
+      lmax = cellfun (@max, lnum, lden, "uniformoutput", false);
+
+      num = cellfun (@postpad, num, lmax, "uniformoutput", false);
+      den = cellfun (@postpad, den, lmax, "uniformoutput", false);
+
+      ## use standard tf constructor
+      ## sys is stored in standard z form, not z^-1
+      ## so we can mix it with regular transfer function models
+      ## property "inv", true displays sys in z^-1 form
+      sys = tf (num, den, tsam, "inv", true, varargin{:});
+  endswitch
+
+endfunction
+
+%!shared num, den, n1, d1, n2, d2, n2e, d2e
+%! num = [0, 3];
+%! den = [1, 4, 2];
+%! sys = filt (num, den);
+%! [n1, d1] = filtdata (sys, "vector");
+%! [n2, d2] = tfdata (sys, "vector");
+%! n2e = [3, 0];
+%! d2e = [1, 4, 2];
+%!assert (n1, num, 1e-4);
+%!assert (d1, den, 1e-4);
+%!assert (n2, n2e, 1e-4);
+%!assert (d2, d2e, 1e-4);