[R] sbrier (Brier score) and coxph

[Prof Brian Ripley]

Is this sbrier from package ipred?

The short answer is that it contains

     ptype <- class(pred)

and assumes that is of length one.  For a survfit.coxph fit it is of class
c("survfit.cox", "survfit").  I suspect from the help page that this is 
not supported, but you need to contact the authors (as the posting guide 
suggests).

On Wed, 29 Jun 2005, Stephen Henderson wrote:

> Hello
> I've decided to try and distill an earlier rather ill focused question to
> try and elicit a response. Any help is greatly appreciated. Why does mod.cox
> not work with sbrier whilst mod.km does? Can I make it work?
>
>
>
>> data(DLBCL)
>> DLBCL.surv<-Surv(DLBCL$time,DLBCL$cens)
>>
>> mod.km<-survfit(DLBCL.surv)
>> mod.cox<-survfit(coxph(DLBCL.surv~IPI, data=DLBCL))
>>
>>
>> sbrier(DLBCL.surv, mod.km)
> integrated Brier score
>             0.2076454
> attr(,"time")
> [1]   1.3 129.9
>> sbrier(DLBCL.surv, mod.cox)
> Error in switch(ptype, survfit = { : switch: EXPR must return a length 1
> vector
>
> Thanks in advance
> Stephen Henderson
>
>
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595