Skip to main content
Cross Validated

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

5
  • $\begingroup$ This seems like a major disadvantage of R compared to SAS, which offers a large variety of choices. But I wonder if there is a work around. $\endgroup$ Commented Dec 3, 2023 at 11:36
  • 3
    $\begingroup$ @PeterFlom This is a limitation of the lme4 package, not of $\textsf{R}$. Other package, such as nlme, implement R-side effects or covariance structures. $\endgroup$ Commented Dec 3, 2023 at 13:09
  • $\begingroup$ @statmerkur That makes sense and is good to know. I've retired, but when I was working, I mostly used SAS. These days, I don't have access to it (it's expensive) and my R knowledge is somewhat lacking. $\endgroup$ Commented Dec 3, 2023 at 13:21
  • $\begingroup$ @PeterFlom I have also read that by fitting random slopes for the time variable, this results in something similar to an AR1 structure. I have probably got that wrong (AR1 that is), I'm not entirely sure what exactly it does do (that was going to be the subject of a further question. I just didn't want to ask too much in one go!) $\endgroup$ Commented Dec 3, 2023 at 16:53
  • 1
    $\begingroup$ I've seen conflicting information but always assumed lme4 did unstructured only. This page shows how you can trick it into fitting certain structured covariances - never tried though & looks complicated. $\endgroup$ Commented Dec 3, 2023 at 18:49