Stata: Count if non-missing across row for certain range - sum

Question

I am trying to count the number of times an event occurred before a particular age. I have data that shows the age at each event over a lifetime (age_at_event1-age_at_event3), as well as the age at which I am no longer interested in counting such events (stop_age). I would like to create a variable (sum_event) which counts the number of times the event of interest occurred prior to the stop age. An example:
ID age_event1 age_event2 age_event3 stop_age sum_event
1 10 17 45 34 2
2 23 31 32 54 3
3 25 55 . 32 1
4 21 . . 22 1
How do I create the appropriate sum_event variable?

Answer 1

If you don't want to reshape your data, then you can loop over variables and count:
clear
set more off
*----- example data -----
input ///
ID age_event1 age_event2 age_event3 stop_age sum_event
1 10 17 45 34 2
2 23 31 32 54 3
3 25 55 . 32 1
4 21 . . 22 1
end
list
*----- what you want -----
gen sumevent2 = 0
foreach var of varlist age_event1 age_event2 age_event3 {
replace sumevent2 = sumevent2 + (`var' < stop_age)
}
list
For numbered variables that follow some pattern, you can try something like:
<snip>
gen sumevent2 = 0
forvalues i = 1/3 {
replace sumevent2 = sumevent2 + (age_event`i' < stop_age)
}
Another way with reshape:
*----- what you want -----
<snip>
reshape long age_event, i(ID) j(j)
bysort ID: egen sumevent2 = total(age_event < stop_age)
reshape wide // if you really need to go back to wide
list