st: svy:probit, margeff and lincom problem

["Dimitriy V. Masterov" <dvmaster@gmail.com>]

I am trying to obtain the correct average marginal effect for age and
its square. I am getting a strange error message after using svy:
probit, margeff,  and lincom, which says that "matrix has missing
values". After looking at the trace, I believe the problem is that the
e(V_srs) matrix is missing. Also, using an ordinary probit seems to
work. Does anyone know of a way to deal with this?

My code is:

use "http://www.stata-press.com/data/r9/nhanes2f.dta";, clear
svy: probit heartatk height weight female black age age2
margeff, at(mean age=20 age2=0) replace
lincom age+2*20*age2

Dimitriy Masterov
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