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st: count number of cases rather than observations


From   "David Winter" <d.l.winter@bham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: count number of cases rather than observations
Date   Thu, 24 Nov 2005 17:50:55 -0000

Hello,

I have some survival data and I want to identify the number of cases
that contribute person-time at risk. I also want to split the case by
age. I -stset- and -stsplit by age (entry to exit) and the by risk
interval:

stset var1 enter(time var2) fail(censor-var) id(id-number)
stsplit ageband at (.....)

stset var3 enter(time var4) fail(censor-var) id(id-number)
stsplit riskint at (....)

for 5 cases I might have the data split as follows:

id-number       ageband        riskint
---------       -------        -------
1               0-4            0-9
1		    5-9		 0-9
1               10-14          10-19
2               0-4            0-9
2               5-9            0-9
3               0-4            0-9
4               0-4            0-9
5               0-4            0-9
5               5-9            0-9
5               10-14          10-19

If I group by 'riskint' I would get the following result based on
observations

Riskint	no of obs (contribute person-time at risk)
-------     ---------
0-9             8
10-19           2

But what I want to identify and record is the no. of cases contributing
person-time at risk in each risk interval.

Riskint      no of cases
-------      -----------
0-9             5
10-19           2

There must be an easy way to do this?

Best wishes,
Dave             

****************************************************
Mr David L. Winter, HNC
I.T. Manager (BCCSS Study)
Department of Public Health & Epidemiology
Room 105, Public Health Building
University of Birmingham
Edgbaston
Birmingham
B15 2TT
UK
tel.: +44 (0)121 414 6766
fax.: +44 (0)121 414 7923
****************************************************


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