/usr/share/octave/packages/control-2.6.2/ctrb.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 | ## Copyright (C) 2009-2014 Lukas F. Reichlin
## Copyright (C) 2009 Luca Favatella <slackydeb@gmail.com>
##
## 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{co} =} ctrb (@var{sys})
## @deftypefnx {Function File} {@var{co} =} ctrb (@var{a}, @var{b})
## Return controllability matrix.
##
## @strong{Inputs}
## @table @var
## @item sys
## @acronym{LTI} model.
## @item a
## State matrix (n-by-n).
## @item b
## Input matrix (n-by-m).
## @end table
##
## @strong{Outputs}
## @table @var
## @item co
## Controllability matrix.
## @end table
##
## @strong{Equation}
## @iftex
## @tex
## $$ C_o = [ B \\ \\ AB \\ \\ A^2B \\ \\ldots \\ A^{n-1}B ] $$
## @end tex
## @end iftex
## @ifnottex
## @example
## 2 n-1
## Co = [ B AB A B ... A B ]
## @end example
## @end ifnottex
## @end deftypefn
## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: October 2009
## Version: 0.3
function co = ctrb (a, b)
if (nargin == 1) # ctrb (sys)
if (! isa (a, "lti"))
error ("ctrb: argument must be an lti system");
endif
[a, b] = ssdata (a);
elseif (nargin == 2) # ctrb (a, b)
if (! is_real_square_matrix (a) || ! is_real_matrix (b) || rows (a) != rows (b))
error ("ctrb: invalid arguments (a, b)");
endif
else
print_usage ();
endif
n = rows (a); # number of states
k = 0:n-1; # exponents for a
tmp = arrayfun (@(x) a^x*b, k, "uniformoutput", false);
co = horzcat (tmp{:});
endfunction
%!assert (ctrb ([1, 0; 0, -0.5], [8; 8]), [8, 8; 8, -4]);
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