Re: st: R: Estimating the probability of censoring

[Michael McCulloch <mm@pinest.org>]

Antoine, I believe you are correct that the predicted baseline 
survival function method is better, and the reason I think so is that 
only with this approach using does the probability of being censored 
arrive at zero after the last subject!




> using predicted baseline survival function sounds like a better idea 
> (from 
> http://www.ats.ucla.edu/stat/stata/seminars/stata_survival/default.htm#graphs) 
> :
>
> stcox drug age, nohr  bases(surv0)
> gen cens_adj2=surv0^(exp(coeff_cens))
>
> list id drug age died cens p_cens cens_adj2 in 40/48, clean noobs
>
>
>     id   drug   age   died        cens     p_cens   cens_a~2
>     40      3    50      0   .58476475   .8601028   .6717925
>     41      3    55      1   .58476475   .9429854   .6465274
>     42      3    57      1   .51166915   .9783332   .5577559
>     43      3    48      0   .51166915   .8290267   .6097336
>     44      3    56      0   .34111277   .9604967   .3796235
>     45      3    60      1   .34111277   1.033855   .3525544
>     46      3    62      0   .22740851   1.072609   .2088839
>     47      3    48      0   .11370426   .8290267   .1545282
>     48      3    52      0           0   .8923438          0
>
>
> Antoine
>
>
> Antoine Terracol wrote:
>
> > Hello _all
> >
> > I might be missing something, but isn't the correct way to do this 
> > more like (the part where I generate cens_adj):
> >
> > sysuse cancer.dta, clear
> > gen id = _n                //  generate individual IDs
> > stset studytime, failure(died==0)        //  note that total 
> > person-time is 744
> > *estimate the unadjusted probability of censoring
> > sts gen cens = s
> > *estimate the adjusted probability of censoring
> > stcox drug age, nohr basec(cum)
> > predict coeff_cens, xb            // predicts linear coefficients 
> > of censoring
> > gen p_cens = exp(coeff_cens)        // adjusted probability of 
> > time-to-censoring
> >
> > gen cens_adj=exp(-cum*exp(coeff_cens))
> >
> > *lists the results
> >
> > list id drug age died cens p_cens cens_adj in 40/48, clean noobs
> >
> >
> >     id   drug   age   died        cens     p_cens   cens_adj
> >     40      3    50      0   .58476475   .8601028   .6811302
> >     41      3    55      1   .58476475   .9429854   .6563864
> >     42      3    57      1   .51166915   .9783332   .5705886
> >     43      3    48      0   .51166915   .8290267   .6216006
> >     44      3    56      0   .34111277   .9604967   .4199265
> >     45      3    60      1   .34111277   1.033855   .3930005
> >     46      3    62      0   .22740851   1.072609   .2585016
> >     47      3    48      0   .11370426   .8290267   .2171345
> >     48      3    52      0           0   .8923438   .0710848
> >
> >
> >
> > Antoine
> *
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