/usr/share/octave/packages/statistics-1.3.0/combnk.m is in octave-statistics 1.3.0-1.
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 | ## Copyright (C) 2010 Soren Hauberg <soren@hauberg.org>
##
## This program 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.
##
## This program 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
## this program; if not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{c} =} combnk (@var{data}, @var{k})
## Return all combinations of @var{k} elements in @var{data}.
## @end deftypefn
function retval = combnk (data, k)
## Check input
if (nargin != 2)
print_usage;
elseif (! isvector (data))
error ("combnk: first input argument must be a vector");
elseif (!isreal (k) || k != round (k) || k < 0)
error ("combnk: second input argument must be a non-negative integer");
endif
## Simple checks
n = numel (data);
if (k == 0 || k > n)
retval = resize (data, 0, k);
elseif (k == n)
retval = data (:).';
else
retval = __combnk__ (data, k);
endif
## For some odd reason Matlab seems to treat strings differently compared to other data-types...
if (ischar (data))
retval = flipud (retval);
endif
endfunction
function retval = __combnk__ (data, k)
## Recursion stopping criteria
if (k == 1)
retval = data (:);
else
## Process data
n = numel (data);
if iscell (data)
retval = {};
else
retval = [];
endif
for j = 1:n
C = __combnk__ (data ((j+1):end), k-1);
C = cat (2, repmat (data (j), rows (C), 1), C);
if (!isempty (C))
if (isempty (retval))
retval = C;
else
retval = [retval; C];
endif
endif
endfor
endif
endfunction
%!demo
%! c = combnk (1:5, 2);
%! disp ("All pairs of integers between 1 and 5:");
%! disp (c);
%!test
%! c = combnk (1:3, 2);
%! assert (c, [1, 2; 1, 3; 2, 3]);
%!test
%! c = combnk (1:3, 6);
%! assert (isempty (c));
%!test
%! c = combnk ({1, 2, 3}, 2);
%! assert (c, {1, 2; 1, 3; 2, 3});
%!test
%! c = combnk ("hello", 2);
%! assert (c, ["lo"; "lo"; "ll"; "eo"; "el"; "el"; "ho"; "hl"; "hl"; "he"]);
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