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annotate scripts/statistics/distributions/pascal_rnd.m @ 3191:e4f4b2d26ee9

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[project @ 1998-10-23 05:43:59 by jwe]
author jwe
date Fri, 23 Oct 1998 05:44:01 +0000
parents
children f8dde1807dee
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3191
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1 ## Copyright (C) 1995, 1996, 1997 Kurt Hornik
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2 ##
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3 ## This program is free software; you can redistribute it and/or modify
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4 ## it under the terms of the GNU General Public License as published by
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5 ## the Free Software Foundation; either version 2, or (at your option)
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6 ## any later version.
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7 ##
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8 ## This program is distributed in the hope that it will be useful, but
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9 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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11 ## General Public License for more details.
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12 ##
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13 ## You should have received a copy of the GNU General Public License
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14 ## along with this file. If not, write to the Free Software Foundation,
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15 ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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16
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17 ## usage: pascal_rnd (n, p [, r, c])
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18 ##
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19 ## pascal_rnd (n, p) returns a matrix of random samples from the Pascal
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20 ## (negative binomial) distribution with parameters n and p. The size of
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21 ## the matrix is the common size of n and p.
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22 ##
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23 ## pascal_rnd (n, p, r, c) returns an r by c matrix of random samples
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24 ## from the Pascal distribution with parameters n and p. Both n and p
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25 ## must be scalar or of size r by c.
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26
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27 ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
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28 ## Description: Random deviates from the Pascal distribution
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29
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30 function rnd = pascal_rnd (n, p, r, c)
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31
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32 if (nargin == 4)
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33 if ( !(is_scalar (r) && (r > 0) && (r == round (r))) )
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34 error ("pascal_rnd: r must be a positive integer");
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35 endif
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36 if ( !(is_scalar (c) && (c > 0) && (c == round (c))) )
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37 error ("pascal_rnd: c must be a positive integer");
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38 endif
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39 [retval, n, p] = common_size (n, p, zeros (r, c));
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40 if (retval > 0)
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41 error (strcat("pascal_rnd: ",
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42 "n and p must be scalar or of size ",
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43 sprintf ("%d by %d", r, c)));
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44 endif
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45 elseif (nargin == 2)
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46 [retval, n, p] = common_size (n, p);
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47 if (retval > 0)
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48 error ("pascal_rnd: n and p must be of common size or scalar");
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49 endif
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50 else
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51 usage ("pascal_rnd (n, p [, r, c])");
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52 endif
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53
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54 [r, c] = size (n);
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55 s = r * c;
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56 n = reshape (n, 1, s);
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57 p = reshape (p, 1, s);
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58 rnd = zeros (1, s);
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59
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60 k = find (!(n > 0) | !(n < Inf) | !(n == round (n)) ...
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61 | !(p <= 0) | !(p >= 1));
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62 if (any (k))
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63 rnd(k) = NaN * ones (1, length (k));
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64 endif
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65
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66 k = find ((n > 0) & (n < Inf) & (n == round (n)) ...
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67 & (p >= 0) & (p <= 1));
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68 if (any (k))
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69 N = max (n(k));
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70 L = length (k);
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71 tmp = floor (log (rand (N, L)) ./ (ones (N, 1) * log (1 - p(k))));
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72 ind = (1 : N)' * ones (1, L);
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73 rnd(k) = sum (tmp .* (ind <= ones (N, 1) * n(k)));
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74 endif
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75
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76 rnd = reshape (rnd, r, c);
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77
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78 endfunction