1 ## Copyright (C) 2006, 2007 Arno Onken <asnelt@asnelt.org>
3 ## This program is free software; you can redistribute it and/or modify it under
4 ## the terms of the GNU General Public License as published by the Free Software
5 ## Foundation; either version 3 of the License, or (at your option) any later
8 ## This program is distributed in the hope that it will be useful, but WITHOUT
9 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
13 ## You should have received a copy of the GNU General Public License along with
14 ## this program; if not, see <http://www.gnu.org/licenses/>.
17 ## @deftypefn {Function File} {[@var{m}, @var{v}] =} poisstat (@var{lambda})
18 ## Compute mean and variance of the Poisson distribution.
20 ## @subheading Arguments
24 ## @var{lambda} is the parameter of the Poisson distribution. The
25 ## elements of @var{lambda} must be positive
28 ## @subheading Return values
32 ## @var{m} is the mean of the Poisson distribution
35 ## @var{v} is the variance of the Poisson distribution
38 ## @subheading Example
42 ## lambda = 1 ./ (1:6);
43 ## [m, v] = poisstat (lambda)
47 ## @subheading References
51 ## Wendy L. Martinez and Angel R. Martinez. @cite{Computational Statistics
52 ## Handbook with MATLAB}. Appendix E, pages 547-557, Chapman & Hall/CRC,
56 ## Athanasios Papoulis. @cite{Probability, Random Variables, and Stochastic
57 ## Processes}. McGraw-Hill, New York, second edition, 1984.
61 ## Author: Arno Onken <asnelt@asnelt.org>
62 ## Description: Moments of the Poisson distribution
64 function [m, v] = poisstat (lambda)
71 if (! isempty (lambda) && ! ismatrix (lambda))
72 error ("poisstat: lambda must be a numeric matrix");
79 # Continue argument check
80 k = find (! (lambda > 0) | ! (lambda < Inf));
89 %! lambda = 1 ./ (1:6);
90 %! [m, v] = poisstat (lambda);
91 %! assert (m, lambda);
92 %! assert (v, lambda);