st: Marginal Effects using subsetted data

["MOSTARDO, NICK" <MOSTARDO@mailbox.sc.edu>]

Hello,

I am running an ordered probit model using data that I wish to subset by
gender and race (both dichotomous measures). I am running the following
commands:

'by gender race, sort: ologit depvar indvars'

At that point, I get the correct output of 4 tables for the proper
combinations of the sorted variables (0,0)(0,1)(1,0)(1,1); however, when
I try to run marginal effects as:

'mfx, predict(p outcome(1))' (my depvar is 3 ordered categories)

I get the error:

'no observations
r(2000);'

I know whatever I am doing wrong is probably something minute, but I
have not been able to lock it down. Is there are way to get STATA to
output marginal effects tables that correspond to the four oprobit
coefficient tables outputted earlier using the "by" command? I have
tried using the 'mfx' command with the 'by' command, but that seems to
give an error:

'mfx may not be combined with by'

Any help would be greatly appreciated.

Thanks,

Nicholas A. Mostardo
Graduate Student
Department of Political Science
304B Gambrell Hall
University of South Carolina
Columbia, SC 29208
630-267-5352 (phone)
803-777-8255 (fax)


*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/