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st: -warning: variables in at() list not found in model after mfx or mfx2

From   Mirko <>
Subject   st: -warning: variables in at() list not found in model after mfx or mfx2
Date   Fri, 20 Jul 2007 17:27:31 +0200

Dear all,

I am trying to estimate marginal effects after -regoprob-. I need to
estimate marginal effects at some specific values of my dependent

So let's say I estimated the following model:

regoprob y x1 x2...x40 z1 z2 ... z30, i(pid) npl(x1 x2)

Then I want to get the marginal effects using

mfx2, m varlist(x1) at(z1=0, z2=0,…z10...,z30=0)


mfx, predict(p outcome(1)) varlist(x1) at(z1=0, z2=0,…z10...,z30=0)
mfx, predict(p outcome(2)) varlist(x1) at(z1=0, z2=0,…z10...,z30=0)

Both -mfx2- and –mfx- seem to work, but both the commands return a
warning that reads:

"-warning: variables z10 ...z30 in at() list not found in model-

I checked repeatedly and those variables are (and must be) in the model.

I then wondered if there was a maximum number that could be dealt with
by the -at()- option. Playing with my model I found out that I stop to
get that warning when I have less than 10 variables in -at()-

I was therefore trying to write an example for statalist using some
generated datasets, but no examples display the above behaviour (error
messages), i.e. I never got that warning message and –mfx- or -mfx2-
worked smoothly.

Is it possible that the problem is the actual length of the –at()-
option rather than the number of variables?

Thank you

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