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Re: st: count number of cases rather than observations


From   Eric Cahuzac <cahuzac@toulouse.inra.fr>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: count number of cases rather than observations
Date   Fri, 25 Nov 2005 09:29:58 +0100

David,
try in two steps:

preserve
bysort id-number riskint: keep if _n==1
bysort riskint: count
restore

the count instruction give
------------------------------------
-> riskint = 0-9
   5
------------------------------------
-> riskint = 10-19
   2

not so pretty but working...
Eric


David Winter a écrit :

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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--
______________________________

Eric Cahuzac
Institut National de la Recherche Agronomique (INRA)
Station d'Economie et Sociologie Rurale (ESR)
Chemin de Borde-Rouge - Auzeville
BP 52627, 31326 CASTANET-TOLOSAN CEDEX
Tel. 05.61.28.53.41 (direct)
    05.61.28.53.49 (secrétariat)
Fax. 05.61.28.53.72
e-mail  cahuzac@toulouse.inra.fr
http://www.toulouse.inra.fr/esr

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