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Re: st: Multiple record per individual data: Counting frequency in which an individual changes from one variable value to another
From
Nick Cox <[email protected]>
To
[email protected]
Subject
Re: st: Multiple record per individual data: Counting frequency in which an individual changes from one variable value to another
Date
Sat, 6 Aug 2011 09:21:54 +0100
bysort study_id : gen different = sum(X != X[_n-1]) & _n > 1)
by study_id : replace different = different[_N]
See -tsspell- from SSC and
SJ-7-2 dm0029 . . . . . . . . . . . . . . Speaking Stata: Identifying spells
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox
Q2/07 SJ 7(2):249--265 (no commands)
shows how to handle spells with complete control over
spell specification
Nick
On Fri, Aug 5, 2011 at 10:04 PM, Weichle, Thomas <[email protected]> wrote:
> I have data which contains multiple records per individual. I have a
> categorical variable X (values 1,2,3) which can vary from record to
> record within the individual. I'd like to know if there is a command
> that will count the number of times in which an individual changes to a
> different value in variable X. Consider the following example:
>
> study_id X
> 100 2
> 100 2
> 100 2
> 100 3
> 555 1
> 555 1
> 555 2
> 555 2
> 555 1
> 555 1
>
> study_id 100 would count as 1 change.
> study_id 555 would count as 2 changes.
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