Mercurial > octave-nkf
view scripts/statistics/distributions/poisson_pdf.m @ 4031:2168f4a0e88d
[project @ 2002-08-10 04:22:52 by jwe]
author | jwe |
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date | Sat, 10 Aug 2002 04:22:52 +0000 |
parents | 38c61cbf086c |
children | 265d566cc770 |
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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, 59 Temple Place - Suite 330, Boston, MA ## 02111-1307, USA. ## -*- texinfo -*- ## @deftypefn {Function File} {} poisson_pdf (@var{x}, @var{lambda}) ## For each element of @var{x}, compute the probability density function ## (PDF) at @var{x} of the poisson distribution with parameter @var{lambda}. ## @end deftypefn ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: PDF of the Poisson distribution function pdf = poisson_pdf (x, l) if (nargin != 2) usage ("poisson_pdf (x, lambda)"); endif [retval, x, l] = common_size (x, l); if (retval > 0) error ("poisson_pdf: x and lambda must be of common size or scalar"); endif [r, c] = size (x); s = r * c; x = reshape (x, 1, s); l = reshape (l, 1, s); pdf = zeros (1, s); k = find (!(l > 0) | isnan (x)); if (any (k)) pdf(k) = NaN * ones (1, length (k)); endif k = find ((x >= 0) & (x < Inf) & (x == round (x)) & (l > 0)); if (any (k)) pdf(k) = exp (x(k) .* log (l(k)) - l(k) - gammaln (x(k) + 1)); endif pdf = reshape (pdf, r, c); endfunction