Dear All,
I met problems when doing contrast and now really need some help in the
model below:

Fit=gam(y~treat+SEQUENCE+PERIOD+SEX+s(x),data=dat,
random=list(SUBJID=~1),correlation=corAR1(form=~1|SUBJID))

And error message keeps coming out when I want to compare the differences
between treatments:

Diff=contrast(Fit,
list(treat=treatment[-placebo.pos]),list(treat="Placebo"),
conf.int=0.9)-- (here
placebo.pos=position of "Placebo" in treatment vector)

I wonder if the function contrast could be used here? If not, what other
options I might have?

I hope it's not a stupid question…

Thanks a lot!

Xia Li

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