Sophie,
I'm myself quite new to linear mixed effect models, but
"PresenceAbsence" sounds like
a binary response variable. So wouldn't be
m1<-lmer(Presencebsence~Habitatype*Width+(1|Sitename),familiy=binomial)
the first thing to try? There is also a special mailing list for linear - mixed
-effect
models:
r-sig-mixed-models at r-project.org
But with numeric problems like this one you really should provide a self
contained
example (i.e. with data), at least the output of str(yourdata), if ever
possible.
Kind regards
Hugo
On Friday 24 June 2011 13:11:23 Sophie Higgins wrote:>
> Hey,
> I am having trouble with lmer. I am looking at the presence/absence of
water shrews against habitat and other factors e.g
> so I used this:
> m1<-lmer(Presencebsence~Habitatype*Width+(1|Sitename))summary(m1)
> But i keep getting this error up
> Error in mer_finalize(ans) : Downdated X'X is not positive definite,
16.> summary(m1)Error in asMethod(object) : matrix is not symmetric [1,2]
> What does this mean and now can I fix it?
> Sophie
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>
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