## root / trunk / src / linad99 / vbeta.cpp @ 1610

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1 | 417 | arnima | ```
/*
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2 | ```
* $Id$
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3 | ```
*
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4 | ```
* Author: David Fournier
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5 | 1112 | johnoel | ```
* Copyright (c) 2008-2012 Regents of the University of California
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6 | 417 | arnima | ```
*/
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7 | ```
/**
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8 | ```
* \file
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9 | ```
* Description not yet available.
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10 | ```
*/
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11 | #include <fvar.hpp> |
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12 | |||

13 | ```
/**
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14 | 1610 | stevenmartell | ```
* Beta density function
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15 | ```
* \param a shape parameter
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16 | ```
* \param b shape parameter
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17 | ```
*
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18 | ```
* Note that the mean of the distribution is given by
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19 | ```
* mu = a/(a+b), and the variance is ab/((a+b)^2 (a+b+1))
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20 | 417 | arnima | ```
*/
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21 | dvariable beta(const prevariable& a,const prevariable& b ) |
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22 | { |
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23 | ```
return exp(gammln(a)+gammln(b)-gammln(a+b));
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24 | } |