st: Using egen and by efficiently when some observations are missing

[Paul Novosad <novosad@gmail.com>]

Dear list,

It often takes me three lines to generate variables based on
conditional group operations using egen.  For example, I want to run
some egen operation on a subset of the data, such as a count.  But I
want the count to exist even when the condition does not hold.  I use
the following:

by country: egen tmp = count(i) if condition == 1
by country: egen count_i = max(tmp)
drop tmp

I write code like this all over the place, and each time it makes my
heart sink.  It feels inefficient but I do not have another solution.
Can someone recommend a more efficient practice?

Thanks,

Paul
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