Hi, William,
Thanks for the reply. For example,
webuse pig
gen drug=.
replace drug=0 if id<=24
replace drug=1 if id>24
gen drug_week=drug*week
xtmixed weight week i.drug drug_week, ||id: week, covariance(unstructured) residuals(independent) mle variance
I want the independent variable 'week' to be random in coefficient and intercept, eg. each id has its own slope and overall, different drug group has different slope at each week. However, if I use the above command, when I run
margins drug, at(week=(1 5 9))
marginsplot
what I got is two straight lines with exactly the same slopes.
The marginsplot I wish to get is the ones in www.stata.com/stata12/margins-plots
Please help.
Thank you very much!
Carol
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