st: How to get marginal effect of quadratic term in tobit model in stata 11.0

[lutunnahar begum <pikitardif@gmail.com>]

Dear all

I am using stata 11.0. I am interested in non-linear effect of some of
the regressors in tobit model....but for tobit, we don't get any
marginal effect for quadratic term. I used the following command:

margins, dydx(*) predict(ystar(0,.)) vce (unconditional) post

But I need marginal effect for tobit model in order to find effect on
observed dependent variable. I am thinking about generating the
squared variable manually and use it as independent variable in tobit,
so that I can get the non-linear effect. But STATA manual suggests
using factor variables (c.x#c.x). Also, I am not quite sure how to
interpret the marginal effect for squared term in tobit model.

What is the proper way to get  marginal effect of quadratic term in
tobit model in stata 11.0?

Thanks for your help.

Regards,
Nahar

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