Thank you very much that's perfect.

Rajen

2009/8/4 Terry Therneau <therneau@mayo.edu>

> > Does anyone know if there is a function like survdiff which can also
> handle
> > left-truncated and right-censored data? When I use it on left-truncated
> and
> > right-censored data I get an error message saying Right censored data
> only.
>
>  coxph(Surv(time1, time2, status) ~ factor(group), data=mydata)
>
>  The 'score' test from a Cox model is identical to the logrank test.
>
>  (Well, almost identical - if there are two deaths on the same day the LR
> calculation uses an n-1 at one point where the Cox uses an n.  Neither is
> right/wrong, just the choice of the authors of the two different papers.
>  The
> difference is never of any consequence, usually several digits out in the
> test
> statistic: just enough to force addendums like this one.)
>
>  To recreate the observed -expected columns
>
>  fit0 <- coxph(Surv(time1, time2, status) ~ factor(group), data=mydata,
>                 iter=0, na.action=na.exclude)
>  o.minus.e <- tapply(resid(fit0), mydata$group, sum)
>  obs       <- tapply(mydata$status, mdata$group, sum)
>  cbind(observed=obs, expected= obs- o.minus.e, "o-e"=o.minus.e)
>
>
>   Terry Therneau
>
>

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