Joseph said
I have a dataset of x-ray records with multiple records per
patient. The records consist of id, age, and sex and I need to know how
many persons had an x-ray when they were between the age of 17 and 25
AND when when they were over 30. My attempts have been crude and I know
there has to be a simple yet elegent way to do this.
I think this should work, without the necessity of reshaping:
bysort id: gen early = inrange(age, 17, 25)
by id: gen late = age > 30
by id: gen both = cond(_n==_N, (sum(early) & sum(late)) , .)
count if both == 1
To test,
set obs 1000
g id=mod(_n,100)+1
g age=40*uniform()
Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html
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