Handling string variables inside collapse command

Question

Edit: I should have generated better data. It isn't necessarily the case that the string variable is destringable. I'm just being lazy here (I don't know how to generate random letters).

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I have a data set with a lot of strings that I want to collapse, but it seems that in general collapse doesn't place nicely with strings, particularly (firstnm) and (count). Here are some similar data.

clear
set obs 9
generate mark = .
replace mark = 1 in 1
replace mark = 2 in 6
generate name = ""
generate random = ""
local i = 0
foreach first in Tom Dick Harry {
    foreach last in Smith Jones Jackson {
        local ++i
        replace name = "`first' `last'" in `i'
        replace random = string(runiform())
    }
}

I want to collapse on "mark", which is simple enough with replace and subscripts.

replace mark = mark[_n - 1] if missing(mark)

But my collapses fail with type mismatch errors.

collapse (firstnm) name (count) random, by(mark)

If I use (first), then the first error clears, but (count) still fails. Is there a solution that avoids an additional by operation?

It seems that the following works, but would also be a lot more time-consuming for my data.

generate nonmissing_random = !missing(random)
egen  nonmissing_random_count = count(nonmissing_random), by(mark)
collapse (first) name nonmissing_random_count, by(mark)

Or is any solution that facilitates using collapse the same?

Answer 1

You can use destring random,replace and then the following works:

collapse (first) name (count) random, by(mark) 

mark    name    random
1   Tom Smith   5
2   Dick Jackson    4

But collapse (firstnm) name (count) random, by(mark) still generates mismatch error.

Answer 2

Thinking on this some more, my egen count with by operation isn't necessary. I can generate a 1/0 variable for nonmissing/missing string variables then use (sum) in collapse.

generate nonmissing_random = !missing(random)
collapse (first) name (sum) nonmissing_random, by(mark)