[R] mcv package gamm function Error in chol(XVX + S)

[Simon Wood]

Dae-Jin,

Thanks for your (offline) persistance: you are right the problem is with 
`gamm'. There was a dimension dropping error in `formXtViX' (called by 
`gamm') for group sizes of 1 (as occurs when you have a random effect per 
observation). This will be fixed in mgcv_1.3-28. 

best,
Simon

On Tuesday 02 October 2007 15:50, Dae-Jin Lee wrote:
> Hi all R users !
>
> I'm using gamm function from Simon Wood's mgcv package, to fit a spatial
> regression Generalized Additive Mixed Model, as covariates I have the
> geographical longitude and latitude locations of indexed data. I include a
> random effect for each district (dist) so the code is
>
> fit <- gamm(y~s(lon,lat,bs="tp", m=2)+offset(log(exp.)),
> random=list(dist=~1), family="poisson", niterPQL=30)
>
> when I run the gamm function I obtain the next error message:
>
> %%%
>  Maximum number of PQL iterations:  30
> iteration 1
> iteration 2
> ...
> iteration 8
> iteration 9
> iteration 10
> Error in chol(XVX + S) : the leading minor of order 29 is not positive
> definite
> %%%
>
> Could be any problem in gamm() ???
>
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-- 
> Simon Wood, Mathematical Sciences, University of Bath, Bath, BA2 7AY UK
> +44 1225 386603  www.maths.bath.ac.uk/~sw283