Attila,

See paper and R code by Millar et al. 2011 for a solution based on 'glm':
http://www.esapubs.org/archive///ecol/E092/146/

Peter

--
Péter Sólymos, Dept Biol Sci, Univ Alberta, T6G 2E9, Canada AB
solymos@ualberta.ca, Ph 780.492.8534, http://psolymos.github.com
Alberta Biodiversity Monitoring Institute, http://www.abmi.ca
Boreal Avian Modelling Project, http://www.borealbirds.ca


On Tue, Dec 3, 2013 at 9:23 AM, Attila Lengyel <lengyel.at@gmail.com> wrote:

> Dear All,
>
> I have a problem with 'betareg' function of 'betareg' package, would you,
> please, help me? I am trying to model compositional similarity on range (0;
> 1) between pairs of sample units as a function of pairwise geographical
> distances, and I often get an error message like this:
>
> "Error in chol.default(K) :
>   the leading minor of order 3 is not positive definite
> In addition: Warning message:
> In sqrt(wpp) : NaNs produced
> Error in chol.default(K) :
>   the leading minor of order 3 is not positive definite
> In addition: Warning messages:
> 1: In betareg.fit(X, Y, Z, weights, offset, link, link.phi, type, control)
> :
>   failed to invert the information matrix: iteration stopped prematurely
> 2: In sqrt(wpp) : NaNs produced"
>
> The problem occurs with any link function. I read that this error is caused
> when my matrix is not positive definite. But how should I avoid this if
> these are the data I have?
>
> Thank you and best regards,
>
> Attila Lengyel
>
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>
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