[R] Multiplying elements of vectors

[Mariana Martinez-Morales]

Super Phil!!
Thank you very much!!

Mariana

On Sat, Feb 5, 2011 at 8:54 PM, Phil Spector <spector at stat.berkeley.edu> wrote:
> 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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>