[R] Concatenation, was Re: Physical Units in Calculations

[Peter Dalgaard]

Stavros Macrakis wrote:

> It would of course be nice if the existing difftime class could be fit
> into this, as it is currently pretty much a second-class citizen.  For
> example, c of two time differences is currently a numeric vector,
> losing its units (hours, days, etc.) completely.

That's actually a generic feature/issue of c(). We also have

 > c(factor(1),factor(3))
[1] 1 1
 > library(survival)
Loading required package: splines
 > c(Surv(1,T),Surv(2,F))
[1] 1 1 2 0

and similar issues apply to rbind() of data frames,

 > rbind(data.frame(s=Surv(1,T)),data.frame(s=Surv(2,F)))
   s.time s.status
1      1        1
2      2        0

There is some potential for redesigning this, using a concat() generic 
which should do the Right Thing for all classed vector-like objects. 
(There is such a function in Splus, but I don't their data frame code is 
using it.)

-- 
    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
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