[R] Problem on glmer

[Dennis Murphy]

Hi:

I believe that the problem with the glmer() call is that you are
invoking the Gamma family, which appears not to be implemented at
present. See

http://r-project.markmail.org/search/?q=r-sig-mixed-models#query:r-sig-mixed-models%20date%3A201105%20+page:8+mid:q2b2uoupejdzmvtl+state:results

Dennis

On Mon, May 16, 2011 at 3:31 PM, Zhang,Yanwei <Yanwei.Zhang at cna.com> wrote:
> Hi all,
>
> I was trying to fit a Gamma hierarchical model using "glmer", but got weird error message that I could not understand. On the other hand, a similar call to the glmmPQL leads to results that are close to what I expect. I also tried to change tha "nAGQ" argument in "glmer", but it did not solve the problem. The model I was fitting has a simple structure - one hierarchy and one offset, and I did not expect "glmer" to fail on this simple data set. Did I specify something wrong here? I appreciate any help. Thanks in advance.
>
> #############################################################
> ## Code to fit the model
> #############################################################
> library(MASS)
> library(lme4)
> address <- "http://instruction.bus.wisc.edu/jfrees/jfreesbooks/Longitudinal%20and%20Panel%20Data/Book/Data/TXTData/WorkerC.txt"
> wc <- read.table(address,header=T)
> # clean data
> cl <- unique(wc$CL[wc$LOSS==0])
> wc2 <- subset(wc, !(CL %in% cl) )
> # fit model
> fit1 <- glmmPQL(LOSS~ YR+offset(log(PR)), random=~1|CL,family=Gamma(link="log"),
>          data=wc2)
> fit2 <- glmer(LOSS~ (1|CL) + YR+offset(log(PR)), family=Gamma(link="log"),
>          data=wc2)
>
>
> #############################################################
> ## Results of fit1 and fit2
> #############################################################
>
>> fit1
> Linear mixed-effects model fit by maximum likelihood
>  Data: wc2
>  Log-likelihood: NA
>  Fixed: LOSS ~ YR + offset(log(PR))
>  (Intercept)            YR
> -4.2830507147  0.0005085944
>
> Random effects:
>  Formula: ~1 | CL
>        (Intercept)  Residual
> StdDev:   0.8313193 0.5346455
>
> Variance function:
>  Structure: fixed weights
>  Formula: ~invwt
> Number of Observations: 700
> Number of Groups: 100
>> fit2
> Error in asMethod(object) : matrix is not symmetric [1,2]
>
>
>
>
> Wayne (Yanwei) Zhang
> Statistical Research
> CNA
> Email: Yanwei.Zhang at cna.com<mailto:Yanwei.Zhang at cna.com>
>
>
>
>
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