[R] Error using betareg

[Achim Zeileis]

On Fri, 24 Jun 2011, oyvfos wrote:

> The replication of the error did not "suceed" because I forgot to tell that
> X2 is a factor. Sorry about that. For instance:
> d[,3]=as.factor(d[,3])
> This piece is just a small sample of a larger error for which I encouneter
> this error many times.

You try to estimate coefficients for levels with very few observations. In 
particular for one level, the number of occurrences is only _one_. This 
creates problems if you want to compute measures of reliability (which are 
required in beta regression residuals).

If you want to get the usual coefficient table with partial Wald tests, 
you can still do so via coeftest(m), as illustrated in the vignette. The 
results will, of course, not be very meaningful for those coefficients 
estimated from just one observation...

However, if you want to have a model that is interpretable as a whole, 
then include only levels whose coefficients can be estimated meaningfully.

In your demo case, you need to exclude at least the level "700".

Best,
Z


> Thanks
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