st: coding question

["Ziad El-Khatib" <Ziad.El-Khatib@ki.se>]

Thank you for the tips about the book, order it and waiting to come.

Question how to calculate variable representing cumulative value 'cumulad'

= [(total n pillmissed per patient at all visits) / (total n pillspres
at all visits)] * 100

example below, any tips?


patientid          visitn          pillspres          pillmissed
   cumulad
------------          -------          ------------
---------------          ------------
1001                 1                 30                     2
1001                 2                 20                     5
1001                 6                 50                     1
1002 etc..



Thank you and best regards
ziad
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