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st: selecting random matched controls: survival


From   Michael McCulloch <mm@pinest.org>
To   Statalist <statalist@hsphsun2.harvard.edu>
Subject   st: selecting random matched controls: survival
Date   Mon, 24 Dec 2007 11:11:38 -0800

Dear Statalist members,

I would like to ask help in a routine for selecting random matched controls in a survival dataset.

I have patients (tx=1) and controls (tx=0), and have _stset_.
Time from diagnosis to death = _t.
In the patients, I also know the time between diagnosis and treatment (leadtime).

I wish to randomly select two controls per patient, from among all controls who have survived at least as long as the leadtime for that patient. For example, subject ID==1 has eligible controls:
ID==12 | ID==13 | ID==14
Therefore, I'd like to randomly select two controls from among those three eligible controls.

ID tx _t leadtime
1 1 1.0 0.4
2 1 1.2 0.3
11 0 0.1
12 0 0.9
13 0 1.1
14 0 0.5

May I ask how this can be done in a do-file or small program?

Happy Holidays to all,

--

Michael McCulloch
Pine Street Foundation
124 Pine St., San Anselmo, CA 94960-2674
Tel: (415) 407-1357
Fax: (415) 485-1065
mcculloch@pinestreetfoundation.org
www.pinestreetfoundation.org
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