st: can factor variables be used with xtdpdsys?

["Gandelman, Nestor" <gandelman@ort.edu.uy>]

Hello,
I'm trying to estimate the marginal effects in a DPD model of a variable 
that appears in the model with an interaction.

I can estimate the model if I generate the interataction before and then 
run the regression. But if I do so Stata does not consider the 
interaction when estimating the marginal effects.

My variable of interest is "profit" that apperars in a regresion alone 
and interacted  with "fsal". When I type:

.xtdpdsys i_k c.profit##c.fsal, lags(1) artest(2)

I get the following error message:

.clprofit##c:  operator invalid

Can someone help me?

Thanks, Nestor
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/