Mercurial > octave-nkf
view scripts/statistics/distributions/binomial_inv.m @ 5307:4c8a2e4e0717
[project @ 2005-04-26 19:24:27 by jwe]
author | jwe |
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date | Tue, 26 Apr 2005 19:24:47 +0000 |
parents | 4b0f3b055331 |
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## Copyright (C) 1995, 1996, 1997 Kurt Hornik ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2, or (at your option) ## any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, write to the Free ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA ## 02110-1301, USA. ## -*- texinfo -*- ## @deftypefn {Function File} {} binomial_inv (@var{x}, @var{n}, @var{p}) ## For each element of @var{x}, compute the quantile at @var{x} of the ## binomial distribution with parameters @var{n} and @var{p}. ## @end deftypefn ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: Quantile function of the binomial distribution function inv = binomial_inv (x, n, p) if (nargin != 3) usage ("binomial_inv (x, n, p)"); endif if (!isscalar (n) || !isscalar (p)) [retval, x, n, p] = common_size (x, n, p); if (retval > 0) error ("binomial_inv: x, n and p must be of common size or scalars"); endif endif sz = size (x); inv = zeros (sz); k = find (!(x >= 0) | !(x <= 1) | !(n >= 0) | (n != round (n)) | !(p >= 0) | !(p <= 1)); if (any (k)) inv(k) = NaN; endif k = find ((x >= 0) & (x <= 1) & (n >= 0) & (n == round (n)) & (p >= 0) & (p <= 1)); if (any (k)) if (isscalar (n) && isscalar (p)) cdf = binomial_pdf (0, n, p) * ones (size(k)); while (any (inv(k) < n)) m = find (cdf < x(k)); if (any (m)) inv(k(m)) = inv(k(m)) + 1; cdf(m) = cdf(m) + binomial_pdf (inv(k(m)), n, p); else break; endif endwhile else cdf = binomial_pdf (0, n(k), p(k)); while (any (inv(k) < n(k))) m = find (cdf < x(k)); if (any (m)) inv(k(m)) = inv(k(m)) + 1; cdf(m) = cdf(m) + binomial_pdf (inv(k(m)), n(k(m)), p(k(m))); else break; endif endwhile endif endif endfunction