/usr/share/octave/packages/control-2.6.2/zpk.m is in octave-control 2.6.2-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 | ## Copyright (C) 2009-2014 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} =} zpk (@var{"s"})
## @deftypefnx {Function File} {@var{z} =} zpk (@var{"z"}, @var{tsam})
## @deftypefnx {Function File} {@var{sys} =} zpk (@var{sys})
## @deftypefnx {Function File} {@var{sys} =} zpk (@var{k})
## @deftypefnx {Function File} {@var{sys} =} zpk (@var{z}, @var{p}, @var{k}, @dots{})
## @deftypefnx {Function File} {@var{sys} =} zpk (@var{z}, @var{p}, @var{k}, @var{tsam}, @dots{})
## @deftypefnx {Function File} {@var{sys} =} zpk (@var{z}, @var{p}, @var{k}, @var{tsam}, @dots{})
## Create transfer function model from zero-pole-gain data.
## This is just a stop-gap compatibility wrapper since zpk
## models are not yet implemented.
##
## @strong{Inputs}
## @table @var
## @item sys
## @acronym{LTI} model to be converted to transfer function.
## @item z
## Cell of vectors containing the zeros for each channel.
## z@{i,j@} contains the zeros from input j to output i.
## In the SISO case, a single vector is accepted as well.
## @item p
## Cell of vectors containing the poles for each channel.
## p@{i,j@} contains the poles from input j to output i.
## In the SISO case, a single vector is accepted as well.
## @item k
## Matrix containing the gains for each channel.
## k(i,j) contains the gain from input j to output i.
## @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
##
## @seealso{tf, ss, dss, frd}
## @end deftypefn
## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: September 2011
## Version: 0.1
function sys = zpk (z = {}, p = {}, k = [], varargin)
switch (nargin)
case 0 # sys = zpk ()
sys = tf ();
return;
case 1 # sys = zpk (sys), sys = zpk (k), s = zpk ("s")
if (isa (z, "lti") || is_real_matrix (z) || ischar (z))
sys = tf (z);
return;
else
print_usage ();
endif
case 2 # z = zpk ("z", tsam)
if (ischar (z) && issample (p, -1))
sys = tf (z, p);
return;
else
print_usage ();
endif
otherwise # sys = zpk (z, p, k, ...)
if (! iscell (z))
z = {z};
endif
if (! iscell (p))
p = {p};
endif
if (! size_equal (z, p, k))
error ("zpk: arguments z, p and k must have equal dimensions");
endif
num = cellfun (@(zer, gain) real (gain * poly (zer)), z, num2cell (k), "uniformoutput", false);
den = cellfun (@(pol) real (poly (pol)), p, "uniformoutput", false);
sys = tf (num, den, varargin{:});
endswitch
endfunction
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