st: RE: creating an index variable: number of presentations to hospital by participant

["Kieran McCaul" <Kieran.McCaul@uwa.edu.au>]

....

You'll need some sort of patient ID that identifies individuals.
Assuming you have that, then:

sort patient_id arrivaldate, stable
by patient_id: gen order=_n


look at -help sort- for an explanation of the option -stable-.

Without this option, sort will randomly order observations with the same
patient_id and arrivaldate.

Of course, if you have the arrival time as well, you could sort on:

sort patient_id arrivaldate arrivaltime, stable


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Alison
McCarthy
Sent: Tuesday, 14 September 2010 9:24 AM
To: stata
Subject: st: creating an index variable: number of presentations to
hospital by participant


Dear statalist,
 
I am working with a large data file containing presentations to a
hospital emergency department (ED). A number of individuals make more
than one presentation, which I have seen via the command 'duplicate'.
The organisation of my data is below: 
 
ARRIVALDATE    repeaters part_ID age DISCHARGEDATE
30-Mar-10       0          70     50   30-Mar-10 
30-Mar-10       0          70     50   30-Mar-10 
31-Mar-10       0          70     50   31-Mar-10 
01-Apr-10       0          70     50   01-Apr-10 
 

As can be seen, this person presented twice to the ED on the one day;
the second person presenting twice in a two-day period.
 
I wish to create a new variable which tells me the number and order (in
terms of date) of presentations for each participant, and would greatly
appreciate some guidance.
 
Kind regards
  		 	   		  
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