I am new to R and mixed modeling. I would appreciate help with the following
analysis.

I am having trouble identifying the sytax needed to fit a longitudinal mixed
model using an auto-regressive (AR1) covariance matrix using library nlme.

In R commander, I have had no problem fitting a longitudinal mixed model
with an unstructured covariance matrix using library lme4 with the following
syntax.

lmer <- lmer(trans ~ time + A + A:time + (time | studyid), data = long)
summary(lmer)
cftest (lmer)

DV = trans (measured at 4 time-points)
IV = time, A (time-variant individual difference variable, measured at 4
time-points)

Can anyone tell me the syntax needed to fit an AR1 covariance matrix?

Thanks.

	[[alternative HTML version deleted]]


