Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/control-2.3.52/@lti/filtdata.m b/octave_packages/control-2.3.52/@lti/filtdata.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{num}, @var{den}, @var{tsam}] =} filtdata (@var{sys})
+## @deftypefnx {Function File} {[@var{num}, @var{den}, @var{tsam}] =} filtdata (@var{sys}, @var{"vector"})
+## Access discrete-time transfer function data in DSP format.
+## Argument @var{sys} is not limited to transfer function models.
+## If @var{sys} is not a transfer function, it is converted automatically.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## Any type of discrete-time LTI model.
+## @item "v", "vector"
+## For SISO models, return @var{num} and @var{den} directly as column vectors
+## instead of cells containing a single column vector.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item num
+## Cell of numerator(s).  Each numerator is 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 possible as well.
+## @item den
+## Cell of denominator(s).  Each denominator is 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 possible as well.
+## @item tsam
+## Sampling time in seconds.  If @var{tsam} is not specified, -1 is returned.
+## @end table
+## @end deftypefn
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: April 2012
+## Version: 0.1
+
+function [num, den, tsam] = filtdata (sys, rtype = "cell")
+
+  if (nargin > 2)
+    print_usage ();
+  endif
+
+  if (! isdt (sys))
+    error ("lti: filtdata: require discrete-time system");
+  endif
+
+  [num, den, tsam] = tfdata (sys);
+  
+  ## make numerator and denominator polynomials equally long
+  ## by adding leading zeros
+  lnum = cellfun (@length, num, "uniformoutput", false);
+  lden = cellfun (@length, den, "uniformoutput", false);
+
+  lmax = cellfun (@max, lnum, lden, "uniformoutput", false);
+
+  num = cellfun (@prepad, num, lmax, "uniformoutput", false);
+  den = cellfun (@prepad, den, lmax, "uniformoutput", false);
+      
+  ## 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);
+
+  if (strncmpi (rtype, "v", 1) && issiso (sys))
+    num = num{1};
+    den = den{1};
+  endif
+
+endfunction