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Re: st: data management - changing every 1st encountered of a str data content of a var


From   "David Elliott" <[email protected]>
To   [email protected]
Subject   Re: st: data management - changing every 1st encountered of a str data content of a var
Date   Tue, 6 Jan 2009 16:05:20 -0400

bw, you have to inform us about any higher order sorting in your data.
 By this I mean, is the data sorted according to subject, subject +
date, etc.?  Can there be more than two treatments for a subject so
that you might require a diathermy[3]?

e.g.

treatment      subject    date
monopolar          1       2006.03.05
bipolar               2       2006.04.11
bipolar               2       2006.05.22
bipolar               2       2006.10.07
monopolar          3       2006.02.15
nodiathrm           4       2006.08.10
diathermy[2]        5       2006.01.23
diathermy[2]        5       2006.03.12
diathermy[2]        5       2006.08.26

This makes a difference, because you are going to be operating on sorted groups.

Here is how you could create a sequence number for each subject and
treatment type (assuming you have a date variable as well), then use
it to change the sequence for diathermy.

bysort subject treatment date : gen tx_seq=_n
replace treatment = "diathermy["+tx_seq+"]" if treatment=="diathermy[2]"

--
David Elliott
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