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Re: st: Difference in values within the same variable
From
Sara Muller <[email protected]>
To
[email protected]
Subject
Re: st: Difference in values within the same variable
Date
Wed, 04 Jan 2012 08:28:53 +0000
Thank you for everyone's helpful comments. I can now identify the people
I need in my analysis sample.
Very best wishes,
Sara
On 03/01/2012 14:28, Nick Cox wrote:
A small extra flourish would be
bysort patid (timesince) : gen selected = timesince[1]< 183
edit if selected
where "183" or any similar value represents six months in days. That
is, if the smallest value of -timesince- is less than six months, then
that patient had two or more prescriptions in a period of six months
or less. Such patients have -selected- 1 and others have -selected- 0.
Nick
On Tue, Jan 3, 2012 at 2:06 PM, Christopher Baum<[email protected]> wrote:
<>
Sara said
I have long data with multiple prescriptions per person. I want to
define the length of time between successive prescriptions (see data
below, which is sorted by patid (person ID) and presc_date (date of
prescription)), with the eventual aim of including in my analysis only
people who received 2 or more prescription within 6 months of each other.
I'm not bothered really how I do this, although I have been trying to do
it by calculating another variable that gives the time from the previous
prescription (within patid). I believe the equivalent command in SPSS is
called a 'lag', but searching for this in Stata doesn't see to have
turned up the right stuff.
--------------
clear all
input patid str9 presc_date
4457 11aug1997
4457 18aug1997
4457 15sep1997
4457 29sep1997
4457 27oct1997
4457 15dec1997
4457 15dec1997
4457 16apr1998
4457 11may1998
end
g rxd = date(presc_date,"DMY")
format rxd %td
bysort patid (rxd): g timesince = rxd[_n] - rxd[_n - 1]
list
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