Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: coding question


From   "Ziad El-Khatib" <Ziad.El-Khatib@ki.se>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: coding question
Date   Mon, 3 Mar 2008 13:31:31 -0800

Hi Maarten,
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


Thank you in advance and best regards
ziad




 On Wed, Jan 30, 2008 at 12:04 AM, Maarten buis <maartenbuis@yahoo.co.uk> wrote:
 > --- Ziad El-Khatib <Ziad.El-Khatib@ki.se> 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/
 >  -----------------------------------------
 >
 >
 >
 >       ___________________________________________________________
 >  Support the World Aids Awareness campaign this month with Yahoo!
For Good http://uk.promotions.yahoo.com/forgood/
 >
 >
 > *
 >  *   For searches and help try:
 >  *   http://www.stata.com/support/faqs/res/findit.html
 >  *   http://www.stata.com/support/statalist/faq
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index