[R] Pairwise combination
dwinsemius at comcast.net
Tue May 11 23:10:44 CEST 2010
On May 11, 2010, at 4:54 PM, Ista Zahn wrote:
> On Tuesday 11 May 2010 4:27:01 pm David Winsemius wrote:
>> On May 11, 2010, at 1:45 PM, chen jia wrote:
>>> Hi there,
>>> I am looking for a function that takes a vector as input and
>>> all pair wise combination of the elements of the input vector.
>>> For example, the input vector is c(1,2,3,4). The output vector is
>>> and 2, 1 and 3, 1 and 4, 2 and 3, 2 and 4, 3 and 4).
>> That's not a vector.
> True, although it is possible the OP wanted paste(combn(1:4, 2)[1,],
> combn(1:4, 2)[2,])
True enough, but then it would look like c("1 and 2", "1 and 3", ...
etc. Or he could have wanted a matrix, or he could have wanted:
or... any one of a number of things. If, as he said, he was already
successful in creating whatever it was that he wanted, then he
_should_ have offered a valid R object, so we wouldn't need to guess.
>>> representation here is generic.
Whatever that meant.
>>> I can use a for loop to do it, but it gets slow when the number of
>>> elements of the input vector is large.
David Winsemius, MD
West Hartford, CT
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