R help - Mar 2010 - Vector multiplication

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, 
kaspar

---------------------------------------------
kaspar bernet kbernet at student.ethz.ch
stationsstrasse 32 8442 hettlingen
tel 052 301 12 33 mobil 079 789 75 61

Try this:

b %o% a

On Wed, Mar 17, 2010 at 3:03 PM, Kaspar Bernet <kbernet at
student.ethz.ch> 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,
> kaspar
>
> ---------------------------------------------
> kaspar bernet kbernet at student.ethz.ch
> stationsstrasse 32 8442 hettlingen
> tel 052 301 12 33 mobil 079 789 75 61
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


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

Tena koe Kaspar

?outer

outer(b, a)
or
b %o% a

HTH ....

Peter Alspach
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Kaspar Bernet
> Sent: Thursday, 18 March 2010 7:03 a.m.
> To: r-help at r-project.org
> Subject: [R] Vector multiplication
> 
> 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,
> kaspar
> 
> ---------------------------------------------
> kaspar bernet kbernet at student.ethz.ch
> stationsstrasse 32 8442 hettlingen
> tel 052 301 12 33 mobil 079 789 75 61
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

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