Assuming that your visitdate variables are sorted from earliest to
latest, how's this?
gen firstdrop = .
forvalues i = 1/19 {
replace firstdrop = visitdate`i' if cd4`i' < 250 & first250 == .
}
If they're not sorted you really should go to long format and sort them
(which would be a reasonable idea here too).
-ml
Polis, Chelsea B. wrote:
Dear Statalisters,
I would like to create a variable in my dataset to indicate the date at
which a subjects CD4 counts dropped below 250. My data is currently in
wide format, and each subject had anywhere from 1 to 19 visits. For each
subject, I have up to 19 variables that indicate cd4 count (i.e., cd41 cd42
cd43 cd44 and so on), and up to 19 variables that indicate visit date
(visitdate1 visitdate2 visitdate3 visitdate4 etc.). I'd like to create a
variable to indicate the first date at which CD4 count dropped below 250,
if it ever dropped below 250.
Any suggestions on how to write such a code?
Many thanks,
Chelsea
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Michael I. Lichter, Ph.D.
Research Assistant Professor & NRSA Fellow
UB Department of Family Medicine / Primary Care Research Institute
UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
Office: CC 125 / Phone: 716-898-4751 / E-Mail: [email protected]
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