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Re: st: Survival analysis - individual survival functions


From   Steven Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Survival analysis - individual survival functions
Date   Wed, 15 Dec 2010 20:09:30 -0500

Paul,

-predict- gives values at the observations after every regression command. To get it for arbitrary values of the inputs, you have to do it yourself. S(t| t_0) = S(t)/S(t_0), and the formulas for S(.) are on page 358 of the Stata Manual (V 11). You can get the linear predictor for any values of the X's with -margins- or -adjust- ( Stata<11). Add the appropriate auxiliary parameters (returned results e(theta), e(aux_p), e(gamma), e(sigma), e(kappa)); your t and t_0; then plug everything into the formulas.

Steve

Steven J. Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax:    206-202-4783

On Dec 15, 2010, at 4:25 PM, Seed, Paul wrote:

Dear all,
Following a parametric survival regression,
I can use -predict- with the -surv- option to get
the survival function; but I only do not seem to have
any choice over when it is calculated for.

The help file promises me values for S(t|t_0),
and I would like to set both t and t_0 myself.
But they seem to be set automatically,
at the time of entry and exit of the subject.

Is there a simple way of doing this?
If not, is there any chance of it being included
in a future version of Stata?

Many thanks.


Paul Seed, Senior Lecturer in Medical Statistics,
020 7188 3642,
paul.seed@kcl.ac.uk,
King's College London, Division of Women's Health
Please do not send unencrypted un-anonymised data to this address.




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