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view main/statistics/inst/lognstat.m @ 2775:0c3a065aa01b octave-forge
Documentation update.
author | whyly |
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date | Wed, 29 Nov 2006 22:53:32 +0000 |
parents | 1a3ee8d558f3 |
children | 73fa4496fb07 |
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## Copyright (C) 2006 Arno Onken ## ## 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 of the License, 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 program; if not, write to the Free Software ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA ## -*- texinfo -*- ## @deftypefn {Function File} {[@var{m}, @var{v}] =} lognstat (@var{mu}, @var{sigma}) ## Returns mean and variance of the lognormal distribution ## ## @subheading Arguments ## ## @itemize @bullet ## @item ## @var{mu} is the first parameter of the lognormal distribution ## ## @item ## @var{sigma} is the second parameter of the lognormal distribution. ## @var{sigma} must be positive or zero ## @end itemize ## @var{mu} and @var{sigma} must be of common size or one of them must be ## scalar ## ## @subheading Return values ## ## @itemize @bullet ## @item ## @var{m} is the mean of the lognormal distribution ## ## @item ## @var{v} is the variance of the lognormal distribution ## @end itemize ## ## @subheading Examples ## ## @example ## @group ## mu = 0:0.2:1; ## sigma = 0.2:0.2:1.2; ## [m, v] = lognstat (mu, sigma) ## @end group ## ## @group ## [m, v] = lognstat (0, sigma) ## @end group ## @end example ## ## @subheading References ## ## @enumerate ## @item ## Wendy L. Martinez and Angel R. Martinez. @cite{Computational Statistics ## Handbook with MATLAB}. Appendix E, pages 547-557, Chapman & Hall/CRC, ## 2001. ## ## @item ## Athanasios Papoulis. @cite{Probability, Random Variables, and Stochastic ## Processes}. McGraw-Hill, New York, second edition, 1984. ## @end enumerate ## @end deftypefn ## Author: Arno Onken <whyly@whyly.org> ## Description: Moments of the lognormal distribution function [m, v] = lognstat (mu, sigma) # Check arguments if (nargin != 2) usage ("[m, v] = lognstat (mu, sigma)"); endif if (! isempty (mu) && ! ismatrix (mu)) error ("lognstat: mu must be a numeric matrix"); endif if (! isempty (sigma) && ! ismatrix (sigma)) error ("lognstat: sigma must be a numeric matrix"); endif if (! isscalar (mu) || ! isscalar (sigma)) [retval, mu, sigma] = common_size (mu, sigma); if (retval > 0) error ("lognstat: mu and sigma must be of common size or scalar"); endif endif # Calculate moments m = exp (mu + (sigma .^ 2) ./ 2); v = (exp (sigma .^ 2) - 1) .* exp (2 .* mu + sigma .^ 2); # Continue argument check k = find (! (sigma >= 0) | ! (sigma < Inf)); if (any (k)) m (k) = NaN; v (k) = NaN; endif endfunction %!test %! mu = 0:0.2:1; %! sigma = 0.2:0.2:1.2; %! [m, v] = lognstat (mu, sigma); %! expected_m = [1.0202, 1.3231, 1.7860, 2.5093, 3.6693, 5.5845]; %! expected_v = [0.0425, 0.3038, 1.3823, 5.6447, 23.1345, 100.4437]; %! assert (m, expected_m, 0.001); %! assert (v, expected_v, 0.001); %!test %! sigma = 0.2:0.2:1.2; %! [m, v] = lognstat (0, sigma); %! expected_m = [1.0202, 1.0833, 1.1972, 1.3771, 1.6487, 2.0544]; %! expected_v = [0.0425, 0.2036, 0.6211, 1.7002, 4.6708, 13.5936]; %! assert (m, expected_m, 0.001); %! assert (v, expected_v, 0.001);