drop observations if certain condition

[Sofia Oliveira]

Hi

How to drop whole "person_id" if for the same treatment there is NOT time = 1 & time = 3 & time = 6 & time = 12 & time = 18? Please see example below:

person_id       treatment           time
      1                 A             1
      1                 A             3
      1                 A             6
      1                 A             12
      1                 A             18
      2                 B             1
      2                 C             3
      2                 C             6
      2                 C             18
      3                 A             6

In this case, I would like to have (dropping all the other observations):

person_id        treatment            time
      1                 A             1
      1                 A             3
      1                 A             6
      1                 A             12
      1                 A             18

Thanks!!

[Nick Cox]

egen wanted = total(inlist(time, 1, 3, 6, 12, 18)), by(person_id) 

keep if wanted == 5

[Sofia Oliveira]

Thank you very much Nick for your quick reply. How to account for the following scenario?

person_id            treatment                time
      1                    A                    3
      1                    A                    6
      1                    A                    12
      1                    B                    1
      1                    B                    18

In this case, person_id has 1,3,6,12,18 but for different treatments. So, in this case I want to drop observations. I need 1,3,6,12,18 for the same treatment.

Thanks a lot!

[Nick Cox]

My error, but clearly you need

 
 egen wanted = total(inlist(time, 1, 3, 6, 12, 18)), by(person_id treatment)

[Sofia Oliveira]

Thank you very much, it works perfectly!