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Re: st: Draw graph after stpiece


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Draw graph after stpiece
Date   Tue, 6 May 2008 17:25:09 +0100 (BST)

--- Thong Pham <T.Pham@rug.nl> wrote:
> Does anybody show me how to draw a hazard, survival function after 
> running stpiece command to estimate a piecewise constant 
> exponential model.

-stpiece- is a user writen program, I assume you the version from -ssc-
(there are sometimes multiple versions of user written software
floating around in cyberspace). Consider the example below: -stpiece-
requires a you -stset- your data using an id variable, which is absent
in the cancer dataset, so I create one with the -gen long id = _n-
command. In order to use postestimation commands you need to specify
the -nopreserve- option in -stpiece-. The hazard is e to the power of
the linear predictor, so the -adjust- commands with the -exp- option
allows you to compute the predicted hazard when for the control group
(_Idrug_2==0 and _Idrug_3==0) with a mean age. Next you graph the
result:

*----------- begin example ----------------------
sysuse cancer, clear
gen long id = _n
stset studytime, failure(died) id(id)
xi: stpiece i.drug age, tp(5 10 20 30) nopreserve
adjust _Idrug_2=0 _Idrug_3=0 age, exp by(studytime) gen(hazard)
twoway line hazard studytime, sort c(J)
*----------- end example ------------------------
(For more on how to use examples I sent to the Statalist, see
http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )

Hope this helps,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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