Hi All

I'm running a mixed-effects model (or multilevel model or growth curve analysis) to estimate trajectories in my outcome variable using multiple imputed data. I know that the margingsplot package does not work with multiple imputed data but I'm trying the following where I plot the model based trajectories using just one of the imputed datasets:

Code:
* my time variable is age, that I centre below so that the model constant is set at age 36. I then create the spline variables for 4 time periods (4 of them):

gen agec=age-36 mkspline age36_43 7 age43_53 17 age53_63 27 age63_69 = agec

br ID agec age36_43 age43_53 age53_63 age63_69 

* The model includes interactions between categorical social class (adultsc) and all 4 spline variables:

mixed score age36_43##i.adultsc age43_53##i.adultsc age53_63##i.adultsc age63_69##i.adultsc i.childsc ib2.education2 sex || NSHD_ID: agec, cov(unstr) mle, if _mi_m==20

* Margins command:

margins adultsc, at(agec=(0 7 17 27 33)) atmeans
marginsplot, noci

The mixed-effects model runs well (no issues).

However, I'm unable to generate the margins for adultsc as I get an error msg saying that 'agec' not found in list of covariates, which is of course true. The splines were based on the variable agec.

So, how would I overcome this problem? I can't include agec in the fixed effects part of the model.

In more general: How would one plots trajectories from a growth curve analysis (mixed effects model) based on multiple imputed data?

Thanks!

Amal