R help - Jan 2010 - confidence intervals for mean (GLM)

Dear useRs,

How could I obtain the confidence intervals for the means of my treatments, when
my data was fitted to a GLM?
I need the CI's for the Poisson and Negative Binomial distributions.

Here's what I have:

mydata1 <- data.frame('treatments'=gl(4,20),
'value'=rpois(80, 1))
model1 <- glm(value ~ treatments, data=mydata1, family=poisson)
means1 <- with(mydata1, tapply(value, treatments, mean))

now I need the confidence intervals for the means

And then again for a negative binomial GLM

require(MASS)
mydata2 <- data.frame('treatments'=gl(4, 4, 64, LETTERS[1:4]),
'species'=gl(4, 1, 64, letters[1:4]), 'value'=rnegbin(64,1,1))
model2 <- glm.nb(value ~ treatments*species, data=mydata2)
means2 <- with(cbind('x'=gl(16,4),mydata2), tapply(value, x, mean))

Can I get the confidence intervals for each mean in means1 and means2, according
to the family used?

Thanks in advance, all the best!
Rafael.


     
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Access the information in

help(predict)
help(fitted)

With your reproducible code, run the following

predict(model1)
predict(model1, type="response")
predict(model1, type="response", se.fit=TRUE)

require(lattice)

xyplot(value+fitted(model1)~treatments, data=mydata1,
       distribute.type=TRUE, type=c("p","a"))

Explore the documentation and examples showed there.

At your disposal.
Walmes.

-----
..oooO
..................................................................................................
..(....)... 0ooo...                              Walmes Zeviani
...\..(.....(.....)...     Master in Statistics and Agricultural
Experimentation
....\_)..... )../....       walmeszeviani at hotmail.com, Lavras - MG, Brasil
............
(_/............................................................................................
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