[R] time as a continuous factor in a linear mixed effects model

Bert Gunter bgunter@4567 @end|ng |rom gm@||@com
Thu Feb 25 18:23:39 CET 2021

You should post this on the r-sig-mixed-models list rather than here.

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Thu, Feb 25, 2021 at 9:20 AM Laura Coco <lauracoco using gmail.com> wrote:

> Hello,
> I am interested in investigating the main effects of group, time, and group
> by time interaction on survey outcomes using linear mixed effects models.
> Time is considered as continuous (number of days since baseline), but isn't
> it also categorical, since I want to compare Session 1 vs Session 4 (for
> example)? How is that handled in the model? As of now, time (days since
> baseline) is being treated as one unit, rather than four separate sessions.
> Here is an example of my code: mdl.outcome <- lmer(outcome ~ time*Group +
> (1 | PID), data = dta)
> Thank you!!
> laura
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