How to make a point estimate in mixed model: the effect of group at a certain point of the slope

[Sanne Bruijniks]

Dear Stata users,

I have a mixed model (see the syntax below) with main effects of group (two dichotomous groups, Groepfreq and Groepbeh), and three effects for time are centered and estimated: a linear, quadratic and cubic line and interactions between them all. Two levels are estimated: measurements in participants.

What I want to know is the effect of group (Groepfreq) at day 90 (linear) or 8100 (quadratic) or 729000 (cubic). I played around with the syntax that is used to make contrasts (contrasts or margins codes) for categorial variables but it doesn't work out and I am stuck. Is it even possible to make a point estimate in a model like this? (in SPSS it is possible, but I like Stata more, so would be very happy if there is a function that can do this)

I am very curious if anybody knows.

Thank you for thinking along,
Best regards,

Sanne

code:
mixed BDI BDIbaseline i.Groepbeh i.Groepfreq c.timedayscentrkwad c.timedayscentered c.timedayscentrkub c.timedayscentrkub#i.Groepfreq c.timedayscentrkub#i.Groepbeh c.timedayscentrkwad#i.Groepfreq c.timedayscentrkwad#i.Groepbeh c.timedayscentered#i.Groepfreq c.timedayscentered#i.Groepbeh,|| ppnr:c.timedayscentered, covariance(unstructured) residuals(ma1, t(Time))

BDI baseline is a covariate
BDI is the dependent variable (8 measurements; Time in the residual covariance structure = time at point 1-8)
Other timevariables are defined as time in days (timedays)
ppnr= subject

[William Lisowski]

You have accidentally been posting your topics in Statalist's Mata Forum, which is used for discussions of Stata's Mata language. While your initial post did get a response, your question will see a much larger audience if you repost it in Statalist's General Forum.

Also, if you have not already done so, please review the Statalist FAQ linked to at the top of this page for posting guidelines and suggestions.

[Sanne Bruijniks]

Sorry! How can I delete the post here?

[William Lisowski]

There is no problem about the post remaining here.

Statalist provides no mechanism for members to delete posts older than a cutoff that's something like one hour. Statalist is meant to act as a discussion forum among its members, not as a "trouble ticket" sort of mechanism, which is why there's no formal way to "close" a topic or delete posts.

What is appropriate is to post a link here, as I do now, directing anyone who finds this topic (perhaps months from now a new member searching the forums for help with a similar problem) to your repost of the question on the General forum at

https://www.statalist.org/forums/for...uous-variables

to see any answers that may have been given there.

Let me add that it would be useful for you to take the time to review the Statalist FAQ linked to from the top of the page, as well as from the Advice on Posting link on the page you used to create your post. Note especially sections 9-12 on how to best pose your question, including posting code more readably by using CODE delimiters.

The more you help others understand your problem, the more likely others are to be able to help you solve your problem.