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st: difficulty determining exposure time for incidence
Hello Stata-listers ---
I'm using Intercooled Stata, version 8.2.
I'm hoping someone can provide some suggestions regarding the
determination of a single value for exposure for each subject
in a dataset. My dataset includes 187 observations (90 unique
values) and I need to determine how many days each subject was
on a particular medication, the problem, however, is that each
subject may be on more than one medication at a time and I do
not want to double-count the number of days on a prescription.
The main problem is that each subject may contain prescriptions
whose dates overlap (or not), and one prescription may envelope
the remaining prescriptions for that person. My dataset
includes a unique identifier, the date the prescription
commenced, the number of days on the medication, and the date
the prescription terminated. My dataset is currently in 'long'
form and each subject appears in the dataset 1-12 times. I've
grappled with this and I suspect that either I need to reshape
the dataset or write a program that loops across observations,
although I'm uncertain whether either approach will accomplish
what I want. Any suggestions?
Many thanks in advance,
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