[R] Sorting Surv objects

[Prof Brian Ripley]

On 12/02/2015 16:26, Professor Bickis wrote:
> It seems that Surv objects do not sort correctly.   This seems to be a bug.  Anyone else found this?

This is presumably about Surv() from package survival, not mentioned.

There was a bug, corrected in R-devel (and I will port to R-patched
before 3.1.3).

However, sorting censored survival events is a matter of definition (in 
?xtfrm but cross-referenced from ?sort) and the definition chosen is not 
that of lifetimes (as deaths at T sort after those alive at T and so 
lived longer).

>> survival.data
> [1] 4+ 3  1+ 2  5+

Please follow the posting guide and give a reproducible example.

library(survival)
d <- Surv(c(2,1,4,3,5), c(1,0,1,0,1))

 > d
[1] 2  1+ 4  3+ 5
 > sort(d)
[1] 1+ 2  3+ 4  5

in R-devel.  But

 > sort(Surv(c(2,2,4,3,5), c(1,0,1,0,1)))
[1] 2+ 2  3+ 4  5

>> class(survival.data)
> [1] "Surv"
>> sort(survival.data)
> [1] 2  1+ 4+ 3  5+
>
> An easy work-around is to define a function sort.Surv
>
> sort.Surv<-function(a){ord<-order(a[,1])
> + a[ord]}
>
>> sort(survival.data)
> [1] 1+ 2  3  4+ 5+
>
> I am using R 3.1.2 GUI 1.65 Mavericks build (6833) running under Yosemite.



-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford
1 South Parks Road, Oxford OX1 3TG, UK