# Re: [R] The math underlying the betareg' package?

From: Gavin Simpson <gavin.simpson_at_ucl.ac.uk>
Date: Thu 18 Jan 2007 - 16:34:04 GMT

On Thu, 2007-01-18 at 20:00 +0530, Ajay Narottam Shah wrote:
> Folks,
>
> The betareg package appears to be polished and works well. But I would
> like to look at the exact formulas for the underlying model being
> estimated, the likelihood function, etc. E.g. if one has to compute
> \frac{\partial E(y)}{\partial x_i}, this requires careful calculations
> through these formulas. I read "Regression analysis of variates
> observed on (0,1): percentages, proportions and fractions", by
> Kieschnick & MucCullogh, Statistical Modelling" 2003, 3:193-213. They
> say that the beta regression that they show is a proposal of theirs -
> is this the same as what betareg does, or is this the Standard
> Formulation?

If you want to know, the best place to look is the source code for the package, available as a tar.gz file from all good CRAN Mirrors.

I suggest this as the Windows binary might not contain the original source (i.e unprocessed with comments etc) - I forget now exactly how the binaries on that platform differ.

The reference cited in the References section of ?betareg would also be a good start, esp to understand what the betareg package is doing and how it compares to the other ref you cite.

HTH G

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