[R] Pairwise combination

[Ista Zahn]

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 generates
> > all pair wise combination of the elements of the input vector.
> 
> ?combn
> 
> > For example, the input vector is c(1,2,3,4). The output vector is c(1
> > 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,], "and", 
combn(1:4, 2)[2,])

-Ista

> 
> > The
> > representation here is generic.
> > 
> > I can use a for loop to do it, but it gets slow when the number of
> > elements of the input vector is large.
> > 
> > Best,
> > Jia
> 
> David Winsemius, MD
> West Hartford, CT
> 
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