[R] Interleaving elements of two vectors?

[(Ted Harding)]

On 25-Mar-10 22:17:23, Rolf Turner wrote:
> 
> I think that
> 
> riffle <- function (a,b) {
> n <- min(length(a),length(b))
> p1 <- as.vector(rbind(a[1:n],b[1:n]))
> p2 <- c(a[-(1:n)],b[-(1:n)])
> c(p1,p2)
> }
> 
> does the trick, and is pretty simple ....
>       cheers,
>               Rolf Turner

The "rbind" step is already quite neat.
But the "c(a[-(1:n)],b[-(1:n)])" is the real magic!
The "trick" of course is that even if length(b) < n,
b[-(1:n)] still makes sense, returning integer(0) which
will not extend anything it is c()'d with.

Nice.
Ted.


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Date: 25-Mar-10                                       Time: 22:47:15
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