[R] Vector multiplication

[Duncan Murdoch]

On 17/03/2010 2:03 PM, Kaspar Bernet wrote:
> Hi, 
> 
> this may sound stupid (and it probably is), but I can't seem to find out how to multiply each element of a vector with each element of another vector where the result would be a matrix of dim[length(vectorOne),length(vectorTwo)] without using loops. 
> 
> example: if
> 
> a -> c(1,2,3)
> b -> c(4,5,6)
> 
> i'm looking for the operation that would yield:
> 
>     [,1] [,2] [,3]
> [1,]    4    8   12
> [2,]    5   10   15
> [3,]    6   12   18
> 
> any hints are greatly appreciated, 

 > a <- 1:3
 > b <- 4:6
 > outer(a,b)
      [,1] [,2] [,3]
[1,]    4    5    6
[2,]    8   10   12
[3,]   12   15   18
 > outer(b,a)
      [,1] [,2] [,3]
[1,]    4    8   12
[2,]    5   10   15
[3,]    6   12   18

Duncan Murdoch