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########################################################################
##
## Copyright (C) 1996-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## 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
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{rnd} =} discrete_rnd (@var{v}, @var{p})
## @deftypefnx {} {@var{rnd} =} discrete_rnd (@var{v}, @var{p}, @var{r})
## @deftypefnx {} {@var{rnd} =} discrete_rnd (@var{v}, @var{p}, @var{r}, @var{c}, @dots{})
## @deftypefnx {} {@var{rnd} =} discrete_rnd (@var{v}, @var{p}, [@var{sz}])
## Return a matrix of random samples from the univariate distribution which
## assumes the values in @var{v} with probabilities @var{p}.
##
## 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 common size of
## @var{v} and @var{p}.
## @end deftypefn
function rnd = discrete_rnd (v, p, varargin)
if (nargin < 2)
print_usage ();
endif
if (! isvector (v))
error ("discrete_rnd: V must be a vector");
elseif (! isvector (p) || (length (p) != length (v)))
error ("discrete_rnd: P must be a vector with length (V) elements");
elseif (any (isnan (p)))
error ("discrete_rnd: P must not have any NaN elements");
elseif (! (all (p >= 0) && any (p)))
error ("discrete_rnd: P must be a nonzero, non-negative vector");
endif
if (nargin == 2)
sz = size (v);
elseif (nargin == 3)
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 ("discrete_rnd: dimension vector must be row vector of non-negative integers");
endif
elseif (nargin > 3)
if (any (cellfun (@(x) (! isscalar (x) || x < 0), varargin)))
error ("discrete_rnd: dimensions must be non-negative integers");
endif
sz = [varargin{:}];
endif
rnd = v(lookup (cumsum (p(1:end-1)) / sum (p), rand (sz)) + 1);
rnd = reshape (rnd, sz);
endfunction
%!assert (size (discrete_rnd (1:2, 1:2, 3)), [3, 3])
%!assert (size (discrete_rnd (1:2, 1:2, [4 1])), [4, 1])
%!assert (size (discrete_rnd (1:2, 1:2, 4, 1)), [4, 1])
## Test class of input preserved
%!assert (class (discrete_rnd (1:2, 1:2)), "double")
%!assert (class (discrete_rnd (single (1:2), 1:2)), "single")
## FIXME: Maybe this should work, maybe it shouldn't.
%!#assert (class (discrete_rnd (1:2, single(1:2))), "single")
## Test input validation
%!error <Invalid call> discrete_rnd ()
%!error <Invalid call> discrete_rnd (1)
%!error discrete_rnd (1:2,1:2, -1)
%!error discrete_rnd (1:2,1:2, ones (2))
%!error discrete_rnd (1:2,1:2, [2 -1 2])
%!error discrete_rnd (1:2,1:2, 1, ones (2))
%!error discrete_rnd (1:2,1:2, 1, -1)
## test v,p verification
%!error discrete_rnd (1, ones (2), ones (2,1))
%!error discrete_rnd (1, ones (2,1), ones (1,1))
%!error discrete_rnd (1, ones (2,1), [1 -1])
%!error discrete_rnd (1, ones (2,1), [1 NaN])
%!error discrete_rnd (1, ones (2,1), [0 0])
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