Stop dofile if drop did not make change

[Felix Stips]

Dear Statalists,

for error-checking in many replace commands, I have found it useful to use the program described in this post: https://www.statalist.org/forums/for...-not-in-a-loop

Does somebody know of a similar solution for drop-commands?

Thank you!

[Maarten Buis]

clear all


program mydrop
    drop `0'
    capture assert r(N_drop) != 0
    if _rc {
        di as err "no observations dropped"
        exit(_rc)
    }
end

sysuse auto
mydrop if foreign == 1
mydrop if foreign == 3

[Felix Stips]

Ah wow, that was easy. I thought I would have to construct the 'N_drop' myself. Thank you!!