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annotate scripts/specfun/betaln.m @ 10358:72fab01e5d68

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improve some size_t queries
author Jaroslav Hajek <highegg@gmail.com>
date Thu, 25 Feb 2010 12:55:13 +0100
parents f0c3d3fc4903
children a8ce6bdecce5
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John W. Eaton <jwe@octave.org>
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1 ## Copyright (C) 1998, 2006, 2007, 2008, 2009 by Nicol N. Schraudolph
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2 ##
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3 ## This file is part of Octave.
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4 ##
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5 ## Octave is free software; you can redistribute it and/or modify it
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6 ## under the terms of the GNU General Public License as published by
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7 ## the Free Software Foundation; either version 3 of the License, or (at
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8 ## your option) any later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 ## General Public License for more details.
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14 ##
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15 ## You should have received a copy of the GNU General Public License
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16 ## along with Octave; see the file COPYING. If not, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Mapping Function} {} betaln (@var{a}, @var{b})
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21 ## Return the log of the Beta function,
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22 ## @tex
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23 ## $$
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24 ## B (a, b) = \log {\Gamma (a) \Gamma (b) \over \Gamma (a + b)}.
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25 ## $$
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26 ## @end tex
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27 ## @ifnottex
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28 ##
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29 ## @example
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30 ## betaln (a, b) = gammaln (a) + gammaln (b) - gammaln (a + b)
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31 ## @end example
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32 ## @end ifnottex
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33 ## @seealso{beta, betainc, gammaln}
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34 ## @end deftypefn
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35
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36 ## Author: Nicol N. Schraudolph <nic@idsia.ch>
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37 ## Created: 06 Aug 1998
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38 ## Keywords: log beta special function
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39
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40 function retval = betaln (a, b)
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41 if (nargin != 2)
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42 print_usage ();
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43 endif
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44
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45 retval = gammaln (a) + gammaln (b) - gammaln (a + b);
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46 endfunction
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47
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48 %!assert (betaln(3,4),log(beta(3,4)),eps)
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49
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50 %!error (betaln(1.))
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51 %!error (betaln(1.,1.,1.))