Create a data subset if one variable takes one specific value at least once

[Ilona Mazmanidou]

Dear community,

I am trying to examine how war affects trade between enemy country pairs. Overall, I have a dataset with 17,407 country pairs. Out of these, some country pairs were engaged in war at one point in time. I am trying to keep those country pair ids, that had war=1 at least once. Can someone help me, please?

So far, I can only keep id if war=1, but I do not wish to keep only wartime trade but all trade for country pairs that had been involved in war at least once.

Thank you!

Best,
Ilona

[Nick Cox]

This sounds like

egen anywar = max(war), by(id)

keep if anywar == 1

See https://www.stata.com/support/faqs/d...ble-recording/

[Ilona Mazmanidou]

Thanks a lot! This was exactly what I was trying to do.