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1 ## Copyright (C) 1995, 1996, 1997, 2005, 2006, 2007 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} {} binoinv (@var{x}, @var{n}, @var{p}) |
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21 ## For each element of @var{x}, compute the quantile at @var{x} of the |
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22 ## binomial distribution with parameters @var{n} and @var{p}. |
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23 ## @end deftypefn |
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24 |
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25 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
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26 ## Description: Quantile function of the binomial distribution |
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27 |
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28 function inv = binoinv (x, n, p) |
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29 |
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30 if (nargin != 3) |
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31 print_usage (); |
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32 endif |
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33 |
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34 if (!isscalar (n) || !isscalar (p)) |
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35 [retval, x, n, p] = common_size (x, n, p); |
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36 if (retval > 0) |
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37 error ("binoinv: x, n and p must be of common size or scalars"); |
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38 endif |
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39 endif |
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40 |
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41 sz = size (x); |
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42 inv = zeros (sz); |
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43 |
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44 k = find (!(x >= 0) | !(x <= 1) | !(n >= 0) | (n != round (n)) |
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45 | !(p >= 0) | !(p <= 1)); |
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46 if (any (k)) |
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47 inv(k) = NaN; |
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48 endif |
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49 |
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50 k = find ((x >= 0) & (x <= 1) & (n >= 0) & (n == round (n)) |
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51 & (p >= 0) & (p <= 1)); |
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52 if (any (k)) |
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53 if (isscalar (n) && isscalar (p)) |
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54 cdf = binopdf (0, n, p) * ones (size(k)); |
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55 while (any (inv(k) < n)) |
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56 m = find (cdf < x(k)); |
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57 if (any (m)) |
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58 inv(k(m)) = inv(k(m)) + 1; |
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59 cdf(m) = cdf(m) + binopdf (inv(k(m)), n, p); |
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60 else |
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61 break; |
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62 endif |
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63 endwhile |
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64 else |
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65 cdf = binopdf (0, n(k), p(k)); |
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66 while (any (inv(k) < n(k))) |
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67 m = find (cdf < x(k)); |
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68 if (any (m)) |
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69 inv(k(m)) = inv(k(m)) + 1; |
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70 cdf(m) = cdf(m) + binopdf (inv(k(m)), n(k(m)), p(k(m))); |
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71 else |
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72 break; |
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73 endif |
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74 endwhile |
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75 endif |
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76 endif |
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77 |
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78 endfunction |
