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1 ## Copyright (C) 1996, 1997, 1998, 2000, 2002, 2004, 2005, 2006, 2007 |
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2 ## Kurt Hornik |
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3 ## |
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4 ## This file is part of Octave. |
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5 ## |
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6 ## Octave is free software; you can redistribute it and/or modify it |
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7 ## under the terms of the GNU General Public License as published by |
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8 ## the Free Software Foundation; either version 3 of the License, or (at |
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9 ## your option) any later version. |
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10 ## |
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11 ## Octave is distributed in the hope that it will be useful, but |
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 ## General Public License for more details. |
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15 ## |
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16 ## You should have received a copy of the GNU General Public License |
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17 ## along with Octave; see the file COPYING. If not, see |
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18 ## <http://www.gnu.org/licenses/>. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} discrete_rnd (@var{n}, @var{v}, @var{p}) |
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22 ## @deftypefnx {Function File} {} discrete_rnd (@var{v}, @var{p}, @var{r}, @var{c}) |
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23 ## @deftypefnx {Function File} {} discrete_rnd (@var{v}, @var{p}, @var{sz}) |
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24 ## Generate a row vector containing a random sample of size @var{n} from |
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25 ## the univariate distribution which assumes the values in @var{v} with |
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26 ## probabilities @var{p}. @var{n} must be a scalar. |
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27 ## |
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28 ## If @var{r} and @var{c} are given create a matrix with @var{r} rows and |
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29 ## @var{c} columns. Or if @var{sz} is a vector, create a matrix of size |
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30 ## @var{sz}. |
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31 ## @end deftypefn |
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32 |
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33 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
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34 ## Description: Random deviates from a discrete distribution |
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35 |
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36 function rnd = discrete_rnd (v, p, r, c) |
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37 |
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38 if (nargin == 4) |
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39 if (! (isscalar (r) && (r > 0) && (r == round (r)))) |
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40 error ("discrete_rnd: r must be a positive integer"); |
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41 endif |
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42 if (! (isscalar (c) && (c > 0) && (c == round (c)))) |
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43 error ("discrete_rnd: c must be a positive integer"); |
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44 endif |
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45 sz = [r, c]; |
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46 elseif (nargin == 3) |
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47 ## A potential problem happens here if all args are scalar, as |
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48 ## we can't distiguish between the command syntax. Thankfully this |
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49 ## case doesn't make much sense. So we assume the first syntax |
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50 ## if the first arg is scalar |
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51 |
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52 if (isscalar (v)) |
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53 sz = [1, floor(v)]; |
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54 v = p; |
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55 p = r; |
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56 else |
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57 if (isscalar (r) && (r > 0)) |
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58 sz = [r, r]; |
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59 elseif (isvector(r) && all (r > 0)) |
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60 sz = r(:)'; |
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61 else |
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62 error ("discrete_rnd: r must be a positive integer or vector"); |
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63 endif |
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64 endif |
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65 else |
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66 print_usage (); |
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67 endif |
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68 |
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69 if (! isvector (v)) |
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70 error ("discrete_rnd: v must be a vector"); |
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71 elseif (! isvector (p) || (length (p) != length (v))) |
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72 error ("discrete_rnd: p must be a vector with length (v) elements"); |
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73 elseif (! (all (p >= 0) && any (p))) |
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74 error ("discrete_rnd: p must be a nonzero, nonnegative vector"); |
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75 endif |
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76 |
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77 rnd = v (lookup (cumsum (p (1 : end-1)) / sum(p), rand (sz)) + 1); |
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78 endfunction |
