# st: Simulation: marginal effect at the 5th percentile

 From "Supnithadnaporn, Anupit" To statalist Subject st: Simulation: marginal effect at the 5th percentile Date Mon, 1 Dec 2008 23:19:12 -0500 (EST)

```Dear all,

I am running a simulation of the logit model. Each repetition I create a variable called
"a", which is normally distributed. I would like to find the marginal effect of this
variable at the certain percentiles of its distribution. The problem is that I cannot
specify the number of the particular percentile in  -mfx, predict(p) at( )-
because I don't know the value in each repetition. So I use the -r( )- from -sum-.
However,my program gives me the error from -mfx- part saying that

'indp5' found where number expected
an error occurred when simulate executed simlognorm

Is there a way to specify the unknown value in -at( )- of -mfx-? Would anybody please help?

Thank you
Anupit

----------------------------------------------------------
program define simnorm, rclass
version 9.0
gen a = sdX1*invnorm(uniform())+ meanX1
sum a, detail
ret scalar ap5 = r(p5)
logit Y a X2 X3, robust
mfx, predict(p) at(mean a=ap5 X2=0)
mat dydxmfx = e(xmfx_dydx)
ret scalar dydxmfxap5 = dydxmfx{1,1]
eret clear
drop a
end

simulate dydxmfxap5 = r(dydxmfxap5), reps(100) saving("C:\data\sima.dta", replace): simnorm
----------------------------------------------------------

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```