[Rd] new behavior in model.response

Berry, Charles ccberry @ending from uc@d@edu
Thu Jun 28 02:06:52 CEST 2018

> On Jun 27, 2018, at 3:58 PM, Achim Zeileis <Achim.Zeileis using uibk.ac.at> wrote:
> On Thu, 28 Jun 2018, Therneau, Terry M., Ph.D. via R-devel wrote:
>> I now understand the issue, which leads to a different and deeper issue which is "how to assign a proper length to Surv objects".
>> > Surv(c(1,2,3), c(1,0,1))
>> [1] 1  2+ 3
>> The above prints as 3 elements and is conceptually 3 elements. But if I give it length method to return a 3 then I need a names method, and names<-  pays no attention to my defined length. How do we conceive of and manage a vector whose elements happen to require more than one storage slot for their representation?  An obvious example is the complex type, but it seems that had to be baked right down into the core.
> I think you just have to implement all methods required to make it look like a vector even if it is internally a matrix. Thus, you need methods for length and for names and names<-. Internally, the names can be stored as row names.

I think a closer look at model.response() would help. 

IIUC, the reasoning therein is that comparing 

	length(data[[1L]]) (aka `length(v)') 


	length(attr(data, "row.names")) (aka `nrows') 

is to decide whether names are sensibly assigned to `v'. I think for Surv objects they are not.

I suppose you could define

	`names<-.Surv` <- function(...) NULL

but that seems so silly I think there must be a better way. 

I am low on coffee right now, but I wonder if having a non-exported version of model.response in the survival package would solve this without breaking anything else. 


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