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.
>
> What else should I be reading about beta regressions? :-)
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
--
%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
Gavin Simpson [t] +44 (0)20 7679 0522
ECRC, UCL Geography, [f] +44 (0)20 7679 0565
Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk
Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/
UK. WC1E 6BT. [w] http://www.freshwaters.org.uk
%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%