How to Determine the Number of Countries in Panel Data for xtsemipar Regression

[Abdullah Ijaz]

Hello StataForum Community,

I am working with panel data and running a semi-parametric regression using the xtsemipar command in Stata. I am interested in finding out the exact number of countries included in my regression sample. Here’s the structure of my command with variable names:
xtsemipar depvar indepvar1 indepvar2 controlvar1 controlvar2 controlvar3, /// nonpar(anonvar) cluster(countryvar) /// ci

Where:

• depvar represents my dependent variable.
• indepvar1 and indepvar2 are my independent variables.
• controlvar1, controlvar2, and controlvar3 are my control variables.
• anonvar is a non-parametric variable.
• countryvar is my country identifier variable.

Could anyone guide me on how to determine the number of unique countries that are included in this regression sample? Is there a specific Stata command or procedure that I can use to get this information.

Any insights or suggestions would be greatly appreciated!

Thank you in advance for your assistance.

[Nick Cox]

SJ-23-2 dm0042_4  . . . . . . . . . . . . . . . . Software update for distinct
        (help distinct, distinctgen if installed)  N. J. Cox and G. M. Longton
        Q2/23   SJ 23(2):595--596
        most important change is addition of distinctgen command

SJ-20-4 dm0042_3  . . . . . . . . . . . . . . . . Software update for distinct
        (help distinct if installed)  . . . . . .  N. J. Cox and G. M. Longton
        Q4/20   SJ 20(4):1028--1030
        sort() option has been added

SJ-15-3 dm0042_2  . . . . . . . . . . . . . . . . Software update for distinct
        (help distinct if installed)  . . . . . .  N. J. Cox and G. M. Longton
        Q3/15   SJ 15(3):899
        improved table format and display of large numbers of
        observations

SJ-12-2 dm0042_1  . . . . . . . . . . . . . . . . Software update for distinct
        (help distinct if installed)  . . . . . .  N. J. Cox and G. M. Longton
        Q2/12   SJ 12(2):352
        options added to restrict output to variables with a minimum
        or maximum of distinct values

SJ-8-4  dm0042  . . . . . . . . . . . .  Speaking Stata: Distinct observations
        (help distinct if installed)  . . . . . .  N. J. Cox and G. M. Longton
        Q4/08   SJ 8(4):557--568
        shows how to answer questions about distinct observations
        from first principles; provides a convenience command

See the 2008 paper for why the term distinct is better than the term unique.