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