R help - Feb 2011 - Multiplying elements of vectors

Hi guys:

Sorry if this question is very basic. I?m learning basic matrix and
vectors multiplication to develop a population matrix model for
plants. I?m trying to multiply the elements of two vectors (each of
the ?x? values by each of the ?y? values) to obtain a square matrix of
xy values.

f.e.
x<-seq(5,205)
y<-seq(5,20,5)
stages<-c(?Sdl?, ?Juv?, ?Ad1?, ?Ad2?)

If I just multiply xy as a matrix
xy<-matrix(x,y,nrow=4,ncol=4,dimnames=list(stages,stages))

I obtain this

xy
        Sdl Juv A1 A2
Sdl   5  10 15 20
Juv   5  10 15 20
A1    5  10 15 20
A2    5  10 15 20

but what I want to obtain is this matrix

        Sdl    Juv     A1    A2
Sdl   25    50      75     100
Juv   50    100    150   200
A1    75    50      225   300
A2    100  200    300   400

Sorry I just sent a message, but I forgot to say thanks for any
suggestion and help!!

Mariana

If the seq(5,205) was a typo, and should have been
seq(5,20,5), then what you're looking for is the outer
product of x and y:
> x = seq(5,20,5)
> y = seq(5,20,5)
> x %o% y
      [,1] [,2] [,3] [,4]
[1,]   25   50   75  100
[2,]   50  100  150  200
[3,]   75  150  225  300
[4,]  100  200  300  400
> outer(x,y)
      [,1] [,2] [,3] [,4]
[1,]   25   50   75  100
[2,]   50  100  150  200
[3,]   75  150  225  300
[4,]  100  200  300  400

The outer() function will accepts a FUN= argument 
which defaults to '*'.

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu


On Sat, 5 Feb 2011, Mariana Martinez-Morales wrote:
> Hi guys:
>
> Sorry if this question is very basic. I?m learning basic matrix and
> vectors multiplication to develop a population matrix model for
> plants. I?m trying to multiply the elements of two vectors (each of
> the ?x? values by each of the ?y? values) to obtain a square matrix of
> xy values.
>
> f.e.
> x<-seq(5,205)
> y<-seq(5,20,5)
> stages<-c(?Sdl?, ?Juv?, ?Ad1?, ?Ad2?)
>
> If I just multiply xy as a matrix
> xy<-matrix(x,y,nrow=4,ncol=4,dimnames=list(stages,stages))
>
> I obtain this
>
> xy
>        Sdl Juv A1 A2
> Sdl   5  10 15 20
> Juv   5  10 15 20
> A1    5  10 15 20
> A2    5  10 15 20
>
> but what I want to obtain is this matrix
>
>        Sdl    Juv     A1    A2
> Sdl   25    50      75     100
> Juv   50    100    150   200
> A1    75    50      225   300
> A2    100  200    300   400
>
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>