RE: [S] combinations

["Ed Callahan" <callahan@envstat.com>]

I quickly got advice from several people in private postings, including
Gabriel Escarela, Colin Mallows, Bill Venables and Roger Koenker.  Dr.
Venables solution has worked perfectly for me:

> subsets <- function(n, k, set = 1:n)
    if(k <= 0) NULL else
      if(k >= n) set else
        rbind(cbind(set[1], Recall(n - 1, k - 1, set[-1])),
        Recall(n - 1, k, set[-1]))

It's a neat example of recursion.  Thanks to all who helped.

Ed

----------------------------------
  Edward Callahan
  Environmental Statistics

  callahan@envstat.com
  http://www.envstat.com
----------------------------------


-----Original Message-----
I need a function that returns a matrix of all the combinations of size k
from n items.  So with n=4 and k=2 I would want

1 2
1 3
1 4
2 3
2 4
3 4

Does anyone know how to achieve this in S-Plus 4.0?

Thanks
Ed

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