[datatable-help] Why does cbind drop key?

[Matthew Dowle]

On Tue, 2011-11-15 at 13:58 +0000, Matthew Dowle wrote:
> Just noticed you said cbind(DT,DF). That has been a saga, see FAQ 2.23,
> but it's ok for now.
> 
> Ok, so we could easily change cbind.data.frame from
> 
> > cbind.data.frame
> function (..., deparse.level = 1)
> {
>     if (inherits(..1, "data.table"))
>         return(data.table(...))
>     data.frame(..., check.names = FALSE)
> }
> 
> to
> 
> > cbind.data.frame
> function (..., deparse.level = 1)
> {
>     if (inherits(..1, "data.table"))
>         return(data.table(...,key=key(..1)))
>     data.frame(..., check.names = FALSE)
> }

Done.

> >> When I do cbind(DT, DF), where DT has a key, the result loses the key.
> >>  cbind can't change ordering though, so why does that happen?  I can
> >> understand if you are trying to combine two keyed DT's that the result
> >> is ambiguous, but it isn't in this case.
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> >>
> >
> >
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> 
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