Pairwise combination

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.

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).

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

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.

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). 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

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.

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

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

Or:

combn(1:4, 2, paste, collapse = ' and ')

On Tue, May 11, 2010 at 5:54 PM, Ista Zahn <istazahn at gmail.com> 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 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

--
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O