[R-sig-eco] Error in solve.default(as.matrix(fit$hessian))

[Highland Statistics Ltd.]

> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 22 Feb 2010 08:06:00 +0100
> From: Roman Lu?trik<roman.lustrik at gmail.com>
> To: r-sig-ecology at r-project.org
> Subject: [R-sig-eco] Error in solve.default(as.matrix(fit$hessian))
> Message-ID:
> 	<63a206011002212306k4c18aa20r173804aa7e9f0ab4 at mail.gmail.com>
> Content-Type: text/plain
>
> Dear list,
>
> I'm trying to construct a zero-inflated negative binomial model but I get
> greeted by an error. I haven't had the chance to try my dataset on different
> OSs or different R version, but I did mange to try that for the "cod
> parasite" data from Zuur et al book (Mixed effect models...) and I get a
> similar error (models with different formulas may or may not go through,
> depending on R  version and the system). This is the error I get for the cod
> data.
>
> 1>  nb1a<- zeroinfl(Intensity ~ Area*Year | Area*Year + Length,
> dist="negbin", link="logit", data=ParasiteCod2)
> Error in solve.default(as.matrix(fit$hessian)) :
>    system is computationally singular: reciprocal condition number =
> 1.5208e-17
>
> I get the same error on my data:
>
> frm<- formula(st_zir ~ obs_b+sonce+mraz+nmv | obs_b+sonce+mraz+nmv)
> nb<- zeroinfl(frm, dist="negbin", link="logit", data=zir2)
> Error in solve.default(as.matrix(fit$hessian)) :
>    system is computationally singular: reciprocal condition number =
> 3.87086e-25
>    

I would suggest to simplify your model (dropping covariates). I guess 
the code has difficulties estimating standard errors, or it may be in a 
local optimum. Or contact the owner of the package.

If some of your covariates are factors with many levels, then this may 
also cause numerical instabilities. Perhaps you can simplify the binary 
part of the model?

Alain


> Has anyone any idea how to solve this? It has been suggested that it's
> something in my data, but I don't know what to think if the cod parasite
> data shows different success/failures on different versions for the same
> model.
>
> Cheers,
> Roman
>
>
>    


-- 


Dr. Alain F. Zuur
First author of:

1. Analysing Ecological Data (2007).
Zuur, AF, Ieno, EN and Smith, GM. Springer. 680 p.
URL: www.springer.com/0-387-45967-7


2. Mixed effects models and extensions in ecology with R. (2009).
Zuur, AF, Ieno, EN, Walker, N, Saveliev, AA, and Smith, GM. Springer.
http://www.springer.com/life+sci/ecology/book/978-0-387-87457-9


3. A Beginner's Guide to R (2009).
Zuur, AF, Ieno, EN, Meesters, EHWG. Springer
http://www.springer.com/statistics/computational/book/978-0-387-93836-3


Other books: http://www.highstat.com/books.htm


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