-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of R. Michael
Weylandt
Sent: Saturday, October 29, 2011 7:46 AM
To: Suleyman K
Cc: r-help at r-project.org
Subject: Re: [R] R help with different combinations of vectors of different sizes
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
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