Looks ok
-- Maarten
--- Ziad El-Khatib <[email protected]> wrote:
> You did kindly answer to this query before, i meant to confirm if i
> want to calculate the cumulative value for first 6 visits only, would
> the command be:
>
> bys id (visitn) : gen cumulad = ///
> sum(pillmissed)/sum(pillspres) * 100, if visitn>=1&visitn<=6
>
> On Wed, Jan 30, 2008 at 12:04 AM, Maarten buis
> > --- 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 )
-----------------------------------------
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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