[R] Surv object in data.frame
tlumley at u.washington.edu
Wed Mar 15 18:23:06 CET 2006
On Wed, 15 Mar 2006, Heinz Tuechler wrote:
> Dear All,
> a Surv object I put in a data frame behaves somehow unexpected (see example).
> If I do a Cox regression on the original Surv object it works. If I put it
> in a data.frame and do the regression on the data frame it does not work.
> Seemingly it has to do with the class attribute, because if I change the
> class attribute to let "Surv" appeare first, again it works.
> Is this known? Should I have found information on it?
Well, this is the sort of thing that happens when you use kludges like
The problem is with [.AsIs
survobj[,1] is supposed to be a vector of times (that's what [.Surv
returns), but [.AsIs sticks the original class attribute on to it.
num [1:5] 0 0 0 0 0
Classes 'AsIs', 'Surv' num [1:5] 0 0 0 0 0
The solution is not to use I() -- there's no problem with putting survival
objects in a data frame
1 (0,1 ] 1
2 (0,2+] 1
3 (0,3 ] 1
4 (0,4 ] 2
5 (0,5 ] 2
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