X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Fm%2Fstatistics%2Fdistributions%2Fchi2rnd.m;fp=octave_packages%2Fm%2Fstatistics%2Fdistributions%2Fchi2rnd.m;h=542ea1de37d5c98e8defd60d8f1107c41b61a665;hp=0000000000000000000000000000000000000000;hb=1c0469ada9531828709108a4882a751d2816994a;hpb=63de9f36673d49121015e3695f2c336ea92bc278

diff --git a/octave_packages/m/statistics/distributions/chi2rnd.m b/octave_packages/m/statistics/distributions/chi2rnd.m
new file mode 100644
index 0000000..542ea1d
--- /dev/null
+++ b/octave_packages/m/statistics/distributions/chi2rnd.m
@@ -0,0 +1,120 @@
+## Copyright (C) 2012 Rik Wehbring
+## Copyright (C) 1995-2012 Kurt Hornik
+##
+## This file is part of Octave.
+##
+## Octave 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.
+##
+## Octave 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 Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {} chi2rnd (@var{n})
+## @deftypefnx {Function File} {} chi2rnd (@var{n}, @var{r})
+## @deftypefnx {Function File} {} chi2rnd (@var{n}, @var{r}, @var{c}, @dots{})
+## @deftypefnx {Function File} {} chi2rnd (@var{n}, [@var{sz}])
+## Return a matrix of random samples from the chi-square distribution with
+## @var{n} degrees of freedom.
+##
+## When called with a single size argument, return a square matrix with
+## the dimension specified.  When called with more than one scalar argument the
+## first two arguments are taken as the number of rows and columns and any
+## further arguments specify additional matrix dimensions.  The size may also
+## be specified with a vector of dimensions @var{sz}.
+## 
+## If no size arguments are given then the result matrix is the size of
+## @var{n}.
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@wu-wien.ac.at>
+## Description: Random deviates from the chi-square distribution
+
+function rnd = chi2rnd (n, varargin)
+
+  if (nargin < 1)
+    print_usage ();
+  endif
+
+  if (nargin == 1)
+    sz = size (n);
+  elseif (nargin == 2)
+    if (isscalar (varargin{1}) && varargin{1} >= 0)
+      sz = [varargin{1}, varargin{1}];
+    elseif (isrow (varargin{1}) && all (varargin{1} >= 0))
+      sz = varargin{1};
+    else
+      error ("chi2rnd: dimension vector must be row vector of non-negative integers");
+    endif
+  elseif (nargin > 2)
+    if (any (cellfun (@(x) (!isscalar (x) || x < 0), varargin)))
+      error ("chi2rnd: dimensions must be non-negative integers");
+    endif
+    sz = [varargin{:}];
+  endif
+
+  if (!isscalar (n) && !isequal (size (n), sz))
+    error ("chi2rnd: N must be scalar or of size SZ");
+  endif
+
+  if (iscomplex (n))
+    error ("chi2rnd: N must not be complex");
+  endif
+
+  if (isa (n, "single"))
+    cls = "single";
+  else
+    cls = "double";
+  endif
+
+  if (isscalar (n))
+    if ((n > 0) && (n < Inf))
+      rnd = 2 * randg (n/2, sz);
+      if (strcmp (cls, "single"))
+        rnd = single (rnd);
+      endif
+    else
+      rnd = NaN (sz, cls);
+    endif
+  else
+    rnd = NaN (sz, cls);
+
+    k = (n > 0) | (n < Inf);
+    rnd(k) = 2 * randg (n(k)/2);
+  endif
+
+endfunction
+
+
+%!assert(size (chi2rnd (2)), [1, 1]);
+%!assert(size (chi2rnd (ones(2,1))), [2, 1]);
+%!assert(size (chi2rnd (ones(2,2))), [2, 2]);
+%!assert(size (chi2rnd (1, 3)), [3, 3]);
+%!assert(size (chi2rnd (1, [4 1])), [4, 1]);
+%!assert(size (chi2rnd (1, 4, 1)), [4, 1]);
+
+%% Test class of input preserved
+%!assert(class (chi2rnd (2)), "double");
+%!assert(class (chi2rnd (single(2))), "single");
+%!assert(class (chi2rnd (single([2 2]))), "single");
+
+%% Test input validation
+%!error chi2rnd ()
+%!error chi2rnd (ones(3),ones(2))
+%!error chi2rnd (ones(2),ones(3))
+%!error chi2rnd (i)
+%!error chi2rnd (1, -1)
+%!error chi2rnd (1, ones(2))
+%!error chi2rnd (1, [2 -1 2])
+%!error chi2rnd (ones(2,2), 3)
+%!error chi2rnd (ones(2,2), [3, 2])
+%!error chi2rnd (ones(2,2), 2, 3)
+