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st: AW: Person-period dataset, stcox, subjects in analysis

From   "Martin Weiss" <>
To   <>
Subject   st: AW: Person-period dataset, stcox, subjects in analysis
Date   Mon, 18 May 2009 09:07:11 +0200


You could also use -estat summ-. -keep-ing as recommended by Jeph tells
Stata to drop every subject not used in the estimation which is a rather
harsh step...

webuse kva, clear
stset failtime
stcox load bearings
estat summ


-----Ursprüngliche Nachricht-----
[] Im Auftrag von MAY BAYDOUN
Gesendet: Montag, 18. Mai 2009 01:33
Betreff: st: Person-period dataset, stcox, subjects in analysis

Dear Statalisters,

This may be a straightforward question with an obvious answer, but I need
your help on it. I have a person-period dataset and I used stset command
specifying origin and id as well as failure and exit. This gave me a
specific number of failures and number of subjects at risk. I ran stcox
using a variable that has missing values for a number of those subjects. I
am trying obtain a selection variable so I can look at baseline
characteristics of those subjects that were selected for this analysis. 
Which of the variables that were generated through the stset command should
I be using for this purpose? 

 stcox x

         failure _d:  failuredem == 2
   analysis time _t:  (age50dem-origin)
             origin:  time origin==1
  enter on or after:  time origin2==1
  exit on or before:  failuredem==1
                 id:  id

Iteration 0:   log likelihood = -1697.8111
Iteration 1:   log likelihood = -1696.3502
Iteration 2:   log likelihood = -1696.3477
Refining estimates:
Iteration 0:   log likelihood = -1696.3477

Cox regression -- Breslow method for ties

No. of subjects =      2321                     Number of obs   =     15721
No. of failures =      270
Time at risk    =  52641.86847
                                                   LR chi2(1)      =
Log likelihood  =   -1696.3477                     Prob > chi2     =

          _t | Haz. Ratio   Std. Err.      z    P>|z|     [95% Conf.
         x|   1.247601    .159471     1.73   0.084     .9711212   1.602796

So, basically, I want to be able to describe the 2,321 subjects in that
analysis. I did that before, but I can't remember how anymore. Thanks for
any help you can provide,



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