Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / statistics-1.1.3 / combnk.m

diff --git a/octave_packages/statistics-1.1.3/combnk.m b/octave_packages/statistics-1.1.3/combnk.m
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+## 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))
+        retval = [retval; C];
+      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"]);