[R] how to get all possible combinations including the diagonal using "combn"

[Marc Schwartz]

On Nov 1, 2010, at 12:46 PM, Louis Plough wrote:

> Hi,
> I am trying to generate all possible permutations (choose 2) of a vector, b,
> for example--using 'combn' the combinations in only one direction are
> generated...
> 
>> b<-c(.1,.2,.3)
>> combn(b,2)
>     [,1] [,2] [,3]
> [1,]  0.1  0.1  0.2
> [2,]  0.2  0.3  0.3
> 
>                        [1,] 0.1  0.2  0.3  0.2  0.3  0.3        These
> should also be there.
>                        [2,] 0.1  0.2  0.3  0.1  0.1  0.2
> 
> Is there another R function that can do this??
> 
> Thanks,
> Louis


See ?expand.grid

b <- c(.1, .2, .3)

> expand.grid(b, b)
  Var1 Var2
1  0.1  0.1
2  0.2  0.1
3  0.3  0.1
4  0.1  0.2
5  0.2  0.2
6  0.3  0.2
7  0.1  0.3
8  0.2  0.3
9  0.3  0.3

HTH,

Marc Schwartz