Suppose you have a list of equal-length numeric vectors and you want to
bind them together in a matrix. You want to a piece of code that will
work no matter how many vectors are in the list. That's what this
construct with do.call() is useful for,
e.g.:
> a <- 1:3
> b <- 4:6
> c <- 7:9
> x1 <- list(a=a,b=b)
> x2 <- list(a=a,b=b,c=c)
> do.call("cbind", x1)
a b
[1,] 1 4
[2,] 2 5
[3,] 3 6
> do.call("cbind", x2)
a b c
[1,] 1 4 7
[2,] 2 5 8
[3,] 3 6 9
>
-- Tony Plate
Leeds, Mark (IED) wrote:
> I did a ?do.call but i don't think i understand it.
>
> if a, b,c,d are numeric vectors then could someone explain the
> difference between
>
> do.call("cbind",list(a,b,c,d))
>
> and cbind(a,b,c,d).
>
> or point to an archive on it.
>
> the return value of cbind is a matrix or dataframe depending on what is
> sent in but i don't
> understand wheen it would be useful to use do.call. i realize it takes a
> list but that's
> all i know about why one use it ? thanks.
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