From: Alberto Monteiro <albmont_at_centroin.com.br>

Date: Mon 16 Oct 2006 - 15:22:04 GMT

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Tue Oct 17 01:54:56 2006

Date: Mon 16 Oct 2006 - 15:22:04 GMT

Grant Izmirlian wrote:

*>
*

> So, Alberto, you didn't see my post?

*>
*

I think I didn't - but you are demanding too much from my memory;
I can hardly remember what I saw yesterday!

> If Y has d independent

*> components that are gamma distributed with common rate and shapes
**> A_1, A_2, ..., A_d, then X, given by the components of Y divided by
**> their sum has distribution Dirichlet(A_1, A_2, ..., A_d). If you
**> want Uniform on the d-simplex, then use A_1 = A_2 = ... = A_d = 1
**> (just as Duncan said)
**>
*

The problem is that I wasn't aware that this was the Dirichlet
distribution [R does not have this distribution, AFAIK, but I
should have consulted the Borg of All Wisdom, the Wikipedia].

Alberto Monteiro

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Tue Oct 17 01:54:56 2006

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