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statisticssequenceanalyticsstata

Find missing instances of a sequence

How can I find in Stata the missing instances of a sequence?

input seq
1
2
4
5
6
7
9
10
end

E.g. 3 and 8 are missing in the sequence 1 to 10. How can they be found?

My attempt

list seq if !inrange(seq, 1,10)

However, this does not work.

Solution

  • Stata uses missing to mean values present in the data with a missing value code.

    Here the problem is to identify values that might have been (should have been?) in the dataset, but are, to use a different word, absent.

    Here are two approaches to your problem:

    clear 
input seq
1
2
4
5
6
7
9
10
end

numlist "1/10" 
local expected `r(numlist)'
levelsof seq, local(observed)
local absent : list expected - observed  

di "`absent'"

forval j = 1/10 {
    quietly count if seq == `j'
    if r(N) == 0 local ABSENT `ABSENT' `j'
}

di "`ABSENT'"