[R-sig-ME] Baseline + Follow-Up

[Douglas Bates]

On Wed, Feb 3, 2010 at 11:12 AM, Isabella Ghement <isabella at ghement.ca> wrote:
> Hi everyone,
>
> I am using the lme() function in the nlme library to fit a linear mixed
> effects model
> such as the one below, where an individual-level follow-up measurement is
> modeled as a linear
> function of an individual-level baseline measurement plus a fixed treatment
> effect
> plus a random cluster effect plus random error:
>
> lme(FollowUp ~ Baseline + Treatment, random=~1|Cluster, method="REML",
> data=Data)
>
> The summary of the lme model fit reports a point estimate and confidence
> interval
> for the treatment effect (i.e., difference in adjusted treatment means), but
> I am also
> interested in getting estimates and confidence intervals for the adjusted
> treatment means.
> In my case, Treatment is a factor having two levels (say, A and B).
> Is there a way to force lme() to report these quantities?

If I understand what you are asking, you can get these standard errors
by modifying the formula to

FollowUp ~ 0 + Treatment + Baseline