[R] Multinomial-Dirichlet using R

David Winsemius dwinsemius at comcast.net
Mon May 13 03:44:02 CEST 2013

On May 12, 2013, at 4:44 PM, Anamika Chaudhuri wrote:

> Hi:
> I have asked this question on Cross-Validated. So it might be a cross
> posting but havent received any responses to it.
> I am trying to see which distribution will best fit the data I am working
> on. The dataset is as following:
>    Site          Nausea      headache        Abdominal Distension
>    1                   17                   5                   10
>    2                    12                   8                   7
>    .....
> So each site has  total # adverse events for each type/category and have
> equal # patients per site, say 60 and there are 63 sites. If I were to
> analyze the data for multiple outcomes per site, the number of events per
> category given the category response rates can be assumed to be
> independently distributed. They can be modeled by a multinomial
> distribution with parameters n=60 and category response rates pi1, . . . ,
> piC for site i. The individual variation in category response rates can be
> modeled by a Dirichlet distribution.
> Just wondering if I am thinking through this correctly.
> If so, could someone share some thoughts on how this could be done in R?

This is more of a statistical question, and I'm surprised no advice was offered on CrossValidated. I responded there. You should find that this sort of question is handled in "S-PLUS (and R) Manual to Accompany Agresti’s Categorical Data Analysis" (2002) 2nd edition by Laura A. Thompson, 2006©, which is very easy to find with a Google search.

David Winsemius
Alameda, CA, USA

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