Interleaving elements of two vectors?

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.


--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 25-Mar-10                                       Time: 22:47:15
------------------------------ XFMail ------------------------------