Could you tell us which version of the lme4 package you are using?
You can just send the output produced by
sessionInfo()
If you can make your data available so we can test it then please do
so. If the data set is large you could send it to me in private email
and I will make it available on a web site.
I think that the development version of the lme4 package, available via
install.packages("lme4", repos = "http://r-forge.r-project.org";)
should be resistant to that type of error but I am willing to be shown
otherwise.
On Thu, Feb 14, 2008 at 10:36 AM, Martijn Vandegehuchte
<[EMAIL PROTECTED]> wrote:
> Dear R-users,
>
> I'm new to R, so my apologies if this question doesn't make sense.
>
> I've tried the following model in lmer, and it works perfectly:
> model<-lmer(aphids~densroot+zone+(1|zone/site), family=quasipoisson)
>
> But if I try the exact same model with a different variable, totmas, the
> model looks as follows:
> model<-lmer(aphids~totmas+zone+(1|zone/site), family=quasipoisson)
>
> Totmas is also a continuous variable just like densroot, but in this case I
> receive the following message:
>
> CHOLMOD warning: &߆e
> Error in objective(.par, ...) :
> Cholmod error `matrix not positive definite' at
> file:../Supernodal/t_cholmod_super_numeric.c, line 613
>
> Moreover, if I test yet another continuous variable "vitality", to my
> surprise R just crashes completely.
>
>
> This is a mystery to me, especially because the variables totmas or vitality
> don't give any problem when I build the exact same models in SAS with proc
> glimmix...
>
> Does someone have experience with this type of problem?
>
> Thank you in advance,
>
> Martijn.
>
>
>
>
> --
> Martijn Vandegehuchte
> Ghent University
> Department Biology
> Terrestrial Ecology Unit
> K.L.Ledeganckstraat 35
> B-9000 Ghent
> telephone: +32 (0)9/264 50 84
> e-mail: [EMAIL PROTECTED]
>
> website TEREC: www.ecology.ugent.be/terec
>
> [[alternative HTML version deleted]]
>
>
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>
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