How to count the number of panels used in the regression

[Olivia Johns]

I have panel-time series. I want to know how many countries (panels) are used in the regression (not observation numbers) after i run the regression.
I can to levelsof country if e(sample) but preferably i want the count of total countries.

Thanks

[Nick Cox]

Various ways.

Note that levelsof in an up-to-date Stata leaves r(r) in its wake. Type

return list

or

di r(r)

to see that number. Otherwise

qui tab country if e(sample) 
di r(r)

is another way to do it.

For yet more, see https://www.stata-journal.com/sjpdf....iclenum=dm0042

[Clyde Schechter]

Also, -xtreg- leaves the number of groups used in the estimation sample in e(N_g).