update packages

[CreaPhase.git] / octave_packages / m / statistics / distributions / trnd.m

diff --git a/octave_packages/m/statistics/distributions/trnd.m b/octave_packages/m/statistics/distributions/trnd.m
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+## 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} {} trnd (@var{n})
+## @deftypefnx {Function File} {} trnd (@var{n}, @var{r})
+## @deftypefnx {Function File} {} trnd (@var{n}, @var{r}, @var{c}, @dots{})
+## @deftypefnx {Function File} {} trnd (@var{n}, [@var{sz}])
+## Return a matrix of random samples from the t (Student) 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 t distribution
+
+function rnd = trnd (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 ("trnd: dimension vector must be row vector of non-negative integers");
+    endif
+  elseif (nargin > 2)
+    if (any (cellfun (@(x) (!isscalar (x) || x < 0), varargin)))
+      error ("trnd: dimensions must be non-negative integers");
+    endif
+    sz = [varargin{:}];
+  endif
+
+  if (!isscalar (n) && !isequal (size (n), sz))
+    error ("trnd: N must be scalar or of size SZ");
+  endif
+
+  if (iscomplex (n))
+    error ("trnd: 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 = randn (sz) ./ sqrt (2*randg (n/2, sz) / n);
+    else
+      rnd = NaN (sz, cls);
+    endif
+  else
+    rnd = NaN (sz, cls);
+
+    k = (n > 0) & (n < Inf);
+    rnd(k) = randn (sum (k(:)), 1) ./ sqrt (2*randg (n(k)/2) ./ n(k))(:);
+  endif
+
+endfunction
+
+
+%!assert(size (trnd (2)), [1, 1]);
+%!assert(size (trnd (ones(2,1))), [2, 1]);
+%!assert(size (trnd (ones(2,2))), [2, 2]);
+%!assert(size (trnd (1, 3)), [3, 3]);
+%!assert(size (trnd (1, [4 1])), [4, 1]);
+%!assert(size (trnd (1, 4, 1)), [4, 1]);
+
+%% Test class of input preserved
+%!assert(class (trnd (1)), "double");
+%!assert(class (trnd (single(1))), "single");
+%!assert(class (trnd (single([1 1]))), "single");
+
+%% Test input validation
+%!error trnd ()
+%!error trnd (1, -1)
+%!error trnd (1, ones(2))
+%!error trnd (i)
+%!error trnd (1, [2 -1 2])
+%!error trnd (1, 2, ones(2))
+%!error trnd (1, 2, -1)
+%!error trnd (ones(2,2), 3)
+%!error trnd (ones(2,2), [3, 2])
+%!error trnd (ones(2,2), 2, 3)
+