[ADMB Users] glmmADMB; offset

Myles Falconer mfalconer at bsc-eoc.org
Tue Nov 9 07:29:10 PST 2010

Hi ADMB users,

I'm new to glmmADMB and R and just have a basic question...

I have owl count data (y) from about 160 routes across Ontario, Canada. I am simply interested in looking at annual indices of owls. My data is overdispersed and zero-inflated, so I would like to fit it to a neg.binomial distribution and also use route as a random effect in the model. I have included an offset in the model since owl counts need to be adjusted according to effort (# of stations sampled)

This is what I have:
fit=glmm.admb(y~yr,random=~1,group="route",data=nswoc,family="nbinom", offset(log(stn)))

My problem is that I don't think the offset for the model is working properly. I get the exact same output with or without the offset included in the model. Am I doing this right? Anyone else have this problem before?

Myles Falconer
Ontario Region Project Biologist,
Bird Studies Canada,
115 Front St., P.O. Box 160,
Port Rowan, ON
N0E 1M0 Canada
Email: mfalconer at birdscanada.org
Ph: 1-888-448-2473 ext. 165
BSC website: http://www.bsc-eoc.org/

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