Dummy Variable matching companies in different groups over time

[Martin Knipp]

Dear Statalist members,

I want to create a dummy variable for examining a subset of my sample.
My sample consists of three groups. There are companies being exposed to an intermediate level of regulation from 2013 to 2016 (segment 1) in a pre period. Then a regulatory change took place. So now there are companies that are exposed to high (segment 2) and low regulation (segment 3) in the 2017 and 2018 post period.

I now want to create the dummy variables pre_high and pre_low. So I want to create a dummy that equals 1 if a company of segment 1 within the pre period has chosen segment 2 in the post period.

I'm kinda stuck right now and not sure how to create such a dummy variable.

Thanks a lot for any suggestions.
Martin

[Carlo Lazzaro]

Martin:
see -help recode-.
Paraphrasing Clyde Schechter 's wise remind that creeps up oftentimes on this forum, whenever you ask for help/advice/code, give an example/excerpt of your data via -dataex-. Thanks.