## Copyright (C) 1995, 1996, 1997 Kurt Hornik ## ## This program 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. ## ## This program 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 this file. If not, write to the Free Software Foundation, ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. ## usage: beta_cdf (x, a, b) ## ## For each element of x, returns the CDF at x of the beta distribution ## with parameters a and b, i.e., PROB( beta(a,b) <= x). ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: CDF of the Beta distribution function cdf = beta_cdf (x, a, b) if (nargin != 3) usage ("beta_cdf (a, b, x)"); endif [retval, x, a, b] = common_size (x, a, b); if (retval > 0) error ("beta_cdf: x, a and b must be of common size or scalar"); endif [r, c] = size (x); s = r * c; x = reshape (x, s, 1); a = reshape (a, s, 1); b = reshape (b, s, 1); cdf = zeros (s, 1); k = find (!(a > 0) | !(b > 0) | isnan (x)); if any (k) cdf (k) = NaN * ones (length (k), 1); endif k = find ((x >= 1) & (a > 0) & (b > 0)); if any (k) cdf (k) = ones (length (k), 1); endif k = find ((x > 0) & (x < 1) & (a > 0) & (b > 0)); if any (k) cdf (k) = betai (a(k), b(k), x(k)); endif cdf = reshape (cdf, r, c); endfunction

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