[R] R help with different combinations of vectors of different sizes

[R. Michael Weylandt]

Just add another outer wrapper:

outer(1:5, outer(1:5, 1:5, "+"), "+")

If you are going to arbitrarily long tuples, it may be worthwhile to
put this in a wrapper like so:

tupleSums <- function(vec, n){
     stopifnot(all.equal(n, as.integer(n)))
     n <- as.integer(n)
     if (n == 1L) return(vec)
     ans <- outer(vec, vec, "+")
     if (n == 2L) return(ans)
     else{
          for (i in 3:n) ans <- outer(vec, ans, "+")
      }
      return(ans)
}

Though this really could be made  much more efficient if you want:
e.g., for the n = 4 case, it would be better to take outer( outer(vec,
vec, "+"), outer(vec, vec, "+"), "+").

Michael

On Sat, Oct 29, 2011 at 9:08 AM, Suleyman K <s.karmv at gmail.com> wrote:
> Hi,
>
> I am trying to get different combinations of a vector of different size and
> find their sum. For example, if I have a vector (i,j) where i and j can be
> anything from 0 to 5, i get these combinations (0,0), (0,1), (1,0), (1,1),
> (2,0), ...... (5,5) and find sum of these as 0, 1, 1, 2, ..... , 10. I used
> outer functions to get this and it worked. What if I have a vector (i,j,k)
> where all i, j , and k can be anything from 0 to 5. I want to do the same
> thing here. Get all the combinations and sum them up. (0,0,0) (0,0,1),
> (0,1,0), (1,0,0), .... (5,5,5) How can I get these combinations and find
> their sums? Thank you very much in advance.
>
> Uka
>
>        [[alternative HTML version deleted]]
>
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