In analysis just do this: read "your datafile name" sort idunique visitdate gen i number = 1 if idunique = idunique[_n-1] then number = number[_n-1] + 1
* now you have a variable "number", which gives the sequence of observations for each person.
select number = 1 * will now make sure you only analyse the first observation.
You may also use the commands aggregate, but there would be a problem (as I remember it) with dates, which are then just integers and no longer dates.
regards Jens Lauritsen EpiData Association
Den 29. sep. 2014, epidata-list@lists.umanitoba.ca skrev:
Hi. I cannot give you the comand syntax in epidata (maybe in Stata) but what you could simply do is the following: Create a variable first_visit_date = min(visit_date) by (id_unique) select where visit_date = firs_visit_date.
Serge
2014-09-29 14:41 GMT+02:00 <epidata-list@lists.umanitoba.ca>:
Dear ALL,
I have a data set where some patients have more than one entry (visit) i.e. same patient with different visit dates, while some have only one entry (visit). I would like to select only the first visit from each patient (The variables to use are id_unique and visit_date)
Regards
Walter _______________________________________________ EpiData-list mailing list EpiData-list@lists.umanitoba.ca http://lists.umanitoba.ca/mailman/listinfo/epidata-list
-- *M. Aymar Serge SOMDA, BEng. MMath. MSPH.* *Méthodologiste - Biostatisticien*
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