st: margins after conditional logit

[Igor Ramzak <igor.ramzak@gmail.com>]

Dear Statalisters,

I am running the -clogit- command in order to explain the probability
on cardiovascular disease.
Two of my explanatory variables are dummies that are mutually
exclusive, sush as age groups and race. These are included in the
estimation using "i.age" and "i.race", so the full model is:

-clogit cv_disease i.age i.race weight weight_squared work-

When I run:
-margins, predict(pu0) dydx(*)-
the table shows for these age and race dummies "(not estimable)".

What is the reason for this error? Where is my mistake? Is there an
alternative way using Stata? Or is it because of the way of estimating
(using clogit)?

Best,
Igor
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