/octave-3.6.2/scripts/statistics/distributions/poissrnd.m

  1## Copyright (C) 2012 Rik Wehbring
  2## Copyright (C) 1995-2012 Kurt Hornik
  3##
  4## This file is part of Octave.
  5##
  6## Octave is free software; you can redistribute it and/or modify it
  7## under the terms of the GNU General Public License as published by
  8## the Free Software Foundation; either version 3 of the License, or (at
  9## your option) any later version.
 10##
 11## Octave is distributed in the hope that it will be useful, but
 12## WITHOUT ANY WARRANTY; without even the implied warranty of
 13## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 14## General Public License for more details.
 15##
 16## You should have received a copy of the GNU General Public License
 17## along with Octave; see the file COPYING.  If not, see
 18## <http://www.gnu.org/licenses/>.
 19
 20## -*- texinfo -*-
 21## @deftypefn  {Function File} {} poissrnd (@var{lambda})
 22## @deftypefnx {Function File} {} poissrnd (@var{lambda}, @var{r})
 23## @deftypefnx {Function File} {} poissrnd (@var{lambda}, @var{r}, @var{c}, @dots{})
 24## @deftypefnx {Function File} {} poissrnd (@var{lambda}, [@var{sz}])
 25## Return a matrix of random samples from the Poisson distribution with
 26## parameter @var{lambda}.
 27##
 28## When called with a single size argument, return a square matrix with
 29## the dimension specified.  When called with more than one scalar argument the
 30## first two arguments are taken as the number of rows and columns and any
 31## further arguments specify additional matrix dimensions.  The size may also
 32## be specified with a vector of dimensions @var{sz}.
 33## 
 34## If no size arguments are given then the result matrix is the size of
 35## @var{lambda}.
 36## @end deftypefn
 37
 38## Author: KH <Kurt.Hornik@wu-wien.ac.at>
 39## Description: Random deviates from the Poisson distribution
 40
 41function rnd = poissrnd (lambda, varargin)
 42
 43  if (nargin < 1)
 44    print_usage ();
 45  endif
 46
 47  if (nargin == 1)
 48    sz = size (lambda);
 49  elseif (nargin == 2)
 50    if (isscalar (varargin{1}) && varargin{1} >= 0)
 51      sz = [varargin{1}, varargin{1}];
 52    elseif (isrow (varargin{1}) && all (varargin{1} >= 0))
 53      sz = varargin{1};
 54    else
 55      error ("poissrnd: dimension vector must be row vector of non-negative integers");
 56    endif
 57  elseif (nargin > 2)
 58    if (any (cellfun (@(x) (!isscalar (x) || x < 0), varargin)))
 59      error ("poissrnd: dimensions must be non-negative integers");
 60    endif
 61    sz = [varargin{:}];
 62  endif
 63
 64  if (!isscalar (lambda) && !isequal (size (lambda), sz))
 65    error ("poissrnd: LAMBDA must be scalar or of size SZ");
 66  endif
 67
 68  if (iscomplex (lambda))
 69    error ("poissrnd: LAMBDA must not be complex");
 70  endif
 71
 72  if (isa (lambda, "single"))
 73    cls = "single";
 74  else
 75    cls = "double";
 76  endif
 77
 78  if (isscalar (lambda))
 79    if (lambda >= 0 && lambda < Inf)
 80      rnd = randp (lambda, sz);
 81      if (strcmp (cls, "single"))
 82        rnd = single (rnd);
 83      endif
 84    else
 85      rnd = NaN (sz, cls);
 86    endif
 87  else
 88    rnd = NaN (sz, cls);
 89
 90    k = (lambda >= 0) & (lambda < Inf);
 91    rnd(k) = randp (lambda(k));
 92  endif
 93
 94endfunction
 95
 96%!assert(size (poissrnd (2)), [1, 1]);
 97%!assert(size (poissrnd (ones(2,1))), [2, 1]);
 98%!assert(size (poissrnd (ones(2,2))), [2, 2]);
 99%!assert(size (poissrnd (1, 3)), [3, 3]);
100%!assert(size (poissrnd (1, [4 1])), [4, 1]);
101%!assert(size (poissrnd (1, 4, 1)), [4, 1]);
102
103%% Test class of input preserved
104%!assert(class (poissrnd (2)), "double");
105%!assert(class (poissrnd (single(2))), "single");
106%!assert(class (poissrnd (single([2 2]))), "single");
107
108%% Test input validation
109%!error poissrnd ()
110%!error poissrnd (1, -1)
111%!error poissrnd (1, ones(2))
112%!error poissrnd (1, 2, ones(2))
113%!error poissrnd (i)
114%!error poissrnd (1, 2, -1)
115%!error poissrnd (1, [2 -1 2])
116%!error poissrnd (ones(2,2), 3)
117%!error poissrnd (ones(2,2), [3, 2])
118%!error poissrnd (ones(2,2), 2, 3)
119
120%!assert (poissrnd (0, 1, 1), 0)
121%!assert (poissrnd ([0, 0, 0], [1, 3]), [0 0 0])
122