--- Ziad El-Khatib <[email protected]> wrote:
> Question how to calculate variable representing cumulative value
> 'cumulad'
>
> = [(total n pillmissed per patient at all visits) / (total n
> pillspres at all visits)] * 100
The trick is to combine -bys- with the -sum- function. -bys id
(visitn)- does whatever folows the : for each person separetely and the
(visitn) ensures that within each person the cases are ordered by
visitn. The -sum- function gives you the cumulative sum. So combining
the two gives you:
*-------------- begin example ------------------
drop _all
input long id visitn pillspres pillmissed
1001 1 30 2
1001 2 20 5
1001 6 50 1
end
bys id (visitn) : gen cumulad = ///
sum(pillmissed)/sum(pillspres) * 100
list
*--------------- end example --------------------
(For more on how to use examples I sent to the Statalist, see
http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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