dirichlet.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>R: Functions for the Dirichlet Distribution</title>
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<table width="100%" summary="page for rdirichlet {gtools}"><tr><td>rdirichlet {gtools}</td><td align="right">R Documentation</td></tr></table>
<h2>Functions for the Dirichlet Distribution</h2>
<h3>Description</h3>
<p>
Functions to compute the density of or generate random deviates from
the Dirichlet distribution.
</p>
<h3>Usage</h3>
<pre>
rdirichlet(n, alpha)
ddirichlet(x, alpha)
</pre>
<h3>Arguments</h3>
<table summary="R argblock">
<tr valign="top"><td><code>x</code></td>
<td>
A vector containing a single random deviate or matrix
containg one random deviate per row.</td></tr>
<tr valign="top"><td><code>n</code></td>
<td>
Number of random vectors to generate. </td></tr>
<tr valign="top"><td><code>alpha</code></td>
<td>
Vector or (for <code>ddirichlet</code>) matrix containing shape
parameters. </td></tr>
</table>
<h3>Details</h3>
<p>
The Dirichlet distribution is the multidimensional generalization of
the beta distribution. It is the canonical Bayesian distribution for
the parameter estimates of a multinomial distribution.
</p>
<h3>Value</h3>
<p>
<code>ddirichlet</code> returns a vector containing the Dirichlet density for the
corresponding rows of <code>x</code>.
<br>
<code>rdirichlet</code> returns a matrix with <code>n</code> rows, each containing
a single Dirichlet random deviate.</p>
<h3>Author(s)</h3>
<p>
Code original posted by Ben Bolker to R-News on Fri Dec 15 2000. See
<a href="http://www.r-project.org/nocvs/mail/r-help/2000/3865.html">http://www.r-project.org/nocvs/mail/r-help/2000/3865.html</a>. Ben
attributed the code to Ian Wilson <a href="mailto:i.wilson@maths.abdn.ac.uk">i.wilson@maths.abdn.ac.uk</a>.
Subsequent modifications by Gregory R. Warnes
<a href="mailto:warnes@bst.rochester.edu">warnes@bst.rochester.edu</a>.
</p>
<h3>See Also</h3>
<p>
<code><a href="../../stats/html/Beta.html">dbeta</a></code>, <code><a href="../../stats/html/Beta.html">rbeta</a></code>
</p>
<h3>Examples</h3>
<pre>
x <- rdirichlet(20, c(1,1,1) )
ddirichlet(x, c(1,1,1) )
</pre>
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