Hi Listers,

seems I have forgotten some basics re offset in glm:

data: 
counts (y) from locations off different size (area), 
explanatory variable: x

Model:
y ~ x+offset(area)
Predictions (pred) using Poisson errors

plot(x,y) and points(x,pred) gives neat "line" of estimated values.

However, for ease of understanding graphs are better using plot(x,y/area).

Question:
How to display predictions from the model in the graph (using y/area)?
Plot(x,y/area) with points(x,pred/area) does not give neat line; predicted
values are varying throughout the graph.

My understanding was that offset(area) using glm on poisson constraints
model by area, so pred/area should do the job.

What am I doing wrong, can anyone please clarify?

Thanks Herry

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