finding maximum value that satisfies conditions

[Claire Wladis]

I have been trying to find a solution to this, but haven't found it (or haven't understood that it does what I am looking for when I have seen it), so I am posting here. Apologies if this question is a bit rudimentary!

I have a variable called sequence that takes on integer values 0 to 7. I want to be able to generate some summative information about this by student and term. For example, I can find the maximum value of sequence for each student per term by writing:

bysort StudentID Term : egen maxenrollseq=max( sequence )

This works as intended. But now I want to generate the maximum value of sequence (again by student by term) for which the value of another variable is 1. I just can't figure out how to do this?

For example, considering the follow made up data (where blank cells are missing data):

StudentID	Term	sequence	var
1	1	3	1
1	1	4	0
1	1	4
1	2	4

I would want student 1 to have a value of 3 for the maxseqvar value in term 1, and to have maxseqvar missing for term 2 (so that the new data would be):

StudentID	Term	sequence	var	maxseqvar
1	1	3	1	3
1	1	4	0	3
1	1	4		3
1	2	4

Thanks in advance for any help!

[Clyde Schechter]

bysort StudentID Term : egen maxenrollseq=max(cond(var == 1, sequence, .))

[Nick Cox]

For more on Clyde's approach, see Section 9 of https://journals.sagepub.com/doi/pdf...867X1101100210

The rest of the paper might be interesting or useful.

[Claire Wladis]

Thanks so much, Clyde Schechter and Nick Cox, this did exactly what I needed.