Hello all,

I want to do something pretty theoretically simple (that I used to do myself, but have completely blanked on how to do). I have a panel data set, and I want to create quartiles based on the value of the outcome variable in the period before treatment. The point is to track whether treatment affected units in different quartiles differently, so I want the value of the quartile variable to be the quartile on the period before treatment in all periods (for all observations within a unit). I don't want to create quartiles per period, I want to create quartiles in one period and get the quartile in that period to show as the value of the quartile variable across all periods.

Thank you in advance for any help provided. I don't include a data sample because I don't think it's necessary as this is a general question, but I can add one if need be.