Hi:

Well, you fit a saturated model. How many degrees of freedom do you have
left for error? The fact that the standard errors are so huge relative to
the estimates is a clue.

Taking a look at your data, it's pretty clear that nation 3 is an
outstanding outlier on its own. It is clearly - nay, blatantly - different
from the other nations in the sample. Look at

boxplot(fre ~ nation, data = data_Analysis)
boxplot(sqrt(fre) ~ nation, data = data_Analysis)

the latter to deal with the huge outlier near 1200 in the original data.
Even on the square root scale, nation 3 sticks out like a sore thumb. 43/77
of your responses have zero frequency, so you should probably be looking
into zero-inflated Poisson models and some of its relatives. Here is one
citation to get you started:

http://www.jstatsoft.org/v27/i08/paper

Package VGAM also has functionality to fit these types of models.

Using package sos, I typed

# Install package sos first if you don't have it:
library(sos)
findFn('zero Poisson')

which found 255 matches; you should find several packages that pertain to
zero-inflated/zero-altered Poisson models.

In the absence of the scientific background behind the data, the dominance
of nation 3 may well mask more subtle effects among the other nations, so
you might want to consider analyses with and without nation 3.

HTH,
Dennis

On Tue, Jan 18, 2011 at 5:45 PM, Lao Meng <laomeng.3@gmail.com> wrote:

> Hi all:
> Here's a question about result of loglinear analysis.
> There're 2 factors:area and nation.The raw data is in the attachment.
>
> I fit the saturated model of loglinear with the command:
> glm_sat<-glm(fre~area*nation, family=poisson, data=data_Analysis)
>
> After that,I extract the coefficients:
> result_sat<-summary(glm_sat)
> result_coe<-result_sat$coefficients
>
> I find that all the coeffients are 1 or very near to 1.
>
> How does this happen?Why all the coeffients are 1 or very near to 1?
>
> Thanks!
>
> My best
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

	[[alternative HTML version deleted]]

