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R: st: R: Someone help me on the multiple failure duration model?


From   "Carlo Lazzaro" <carlo.lazzaro@tiscalinet.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   R: st: R: Someone help me on the multiple failure duration model?
Date   Mon, 3 Nov 2008 18:43:04 +0100

Dear Martin, 
I tried to load the excerpt of the data set provided in your previous message. Whereas Cox proportional hazard model seems to hold (please, see -estat phtest-), the Gamma generalized regression for finding which parametric survival model fits best with your data, doesn't converge (please, see the error message).

stset year, id(id) failure(health_state==1) exit(time .) scale(1)

                id:  id
     failure event:  health_state == 1
obs. time interval:  (year[_n-1], year]
 exit on or before:  time .

------------------------------------------------------------------------------
       21  total obs.
        0  exclusions
------------------------------------------------------------------------------
       21  obs. remaining, representing
        3  subjects
        6  failures in multiple failure-per-subject data
       21  total analysis time at risk, at risk from t =         0
                             earliest observed entry t =         0
                                  last observed exit t =         7

stcox female weight, schoenfeld(sch*)

         failure _d:  health_state == 1
   analysis time _t:  year
  exit on or before:  time .
                 id:  id

Iteration 0:   log likelihood = -5.7807435
Iteration 1:   log likelihood = -4.7542542
Iteration 2:   log likelihood = -4.7462302
Iteration 3:   log likelihood =  -4.746223
Refining estimates:
Iteration 0:   log likelihood =  -4.746223

Cox regression -- no ties

No. of subjects =            3                     Number of obs   =        18
No. of failures =            6
Time at risk    =           18
                                                   LR chi2(2)      =      2.07
Log likelihood  =    -4.746223                     Prob > chi2     =    0.3554

------------------------------------------------------------------------------
          _t | Haz. Ratio   Std. Err.      z    P>|z|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
      female |   .2556673   .3192123    -1.09   0.275     .0221264    2.954196
      weight |   1.079909   .0695928     1.19   0.233     .9517721    1.225297
------------------------------------------------------------------------------

. estat phtest

      Test of proportional hazards assumption

      Time:  Time
      ----------------------------------------------------------------
                  |                      chi2       df       Prob>chi2
      ------------+---------------------------------------------------
      global test |                      2.77        2         0.2505
      ----------------------------------------------------------------

streg female weight, dist(gamma)

         failure _d:  health_state == 1
   analysis time _t:  year
  exit on or before:  time .
                 id:  id
<output omitted>
discontinuous region encountered
cannot compute an improvement
r(430);

I cannot rule out the occurrence of some mistakes in my tackling the issues you outlined.

I do hope that it (at least a bit) help.

Kind Regards,
Carlo
-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Martin Wang
Inviato: lunedì 3 novembre 2008 17.03
A: statalist@hsphsun2.harvard.edu; statalist@hsphsun2.harvard.edu
Oggetto: Re: st: R: Someone help me on the multiple failure duration model?

Dear Carlo,

Many thanks for your suggestion. I've just requested the book from other library. But my question is a little bit urgent, if anyone happens to know the answer could you please kindly help.

Thanks!

Martin

======= 2008-11-03 23:40:52 Original Message:=======

>Dear Martin,
>all these topics are covered in Cleves MA, Gould WW, Gutierrez RG. An
>introduction to survival analysis using Stata. Revised edition. College
>Station: Stata Press, 2004.
>
>In my opinion, this is a very "good value for money" textbook.
>
> 
>Kind Regards,
>
>Carlo
>-----Messaggio originale-----
>Da: owner-statalist@hsphsun2.harvard.edu
>[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Martin Wang
>Inviato: luned?3 novembre 2008 16.22
>A: statalist@hsphsun2.harvard.edu
>Oggetto: st: Someone help me on the multiple failure duration model?
>
>/********** This is a html email************************/
>
>Dear all, 
>
>Can someone help me on the multiple failure duration model? For example,
>let's say I have the following data:
>
>
>year             |       1        |         2        |        3         |
>4         |       5          |       6         |      7                  
>patient 1(Female)|weight:50,ill(0)| weight:52,ill(0) |
>weight:53,fine(1)|weight:48,fine(1)|weight:50,ill(0)  |weight:50,ill(0)
>|weight:50,ill(0)
>patient 2(male)  |weight:51,ill(0)| weight:48,ill(0) | weight:60,ill(0) |
>weight:67,ill(0)|weight:78,fine(1) |weight:60,fine(1)| (missing)  
>patient 3(male)  |weight:52,ill(0)| weight:50,fine(1)| (missing)        |
>(missing)       | weight:50,fine(1)| weight:40,ill(0)| weight:60,ill(0) 
>
>
>You see for each patient there are multiple observations, and also there may
>be multiple failures(in this case - getting fine). And also some subject has
>gap in the data, for example patient 3 has gap in year 3 and year 4. I
>wonder whether I can still use streg or stcox for this setting and use ALL
>the observations. For example,
>
>*****************************************************
>stset t, id(patient) failure(fine) exit(time .) noshow
>stcox weight female, r 
>or streg weight female, r
>*****************************************************
>Can anyone kindly help me out? Any suggestions?
>
>Many thanks!!
>
>Martin
>
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