st: help needed with -margeff-

[Lili Yan <lyan16@gmail.com>]

Dear Statalist users,

I am using -margeff- to calculate marginal effect after Probit but
having a problem. I input

margeff, at(mean) dummies(r1 r2 r3) replace

Sometimes it works fine but sometimes it gives me error message like this:

esample() invalid
r(100);

I cannot tell why. Did anybody have this problem before? Could anybody
help? Thanks a lot!

Best,
Lili

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