[R] vectors cross-product V1 x V2

[Eik Vettorazzi]

Hi,
how about this:

mm<-cbind(V1,V2)
xy<-sapply(1:3,function(x)det(mm[-x,])*(2*(x%%2)-1))

#some checks
all.equal(0,as.vector(xy%*%V1))
all.equal(0,as.vector(xy%*%V2))


Am 08.07.2011 08:27, schrieb Bai:
> Hi, everyone,
> 
> I need an efficient way to do vectors cross product in R.
> 
> Set vectors,
> V1 = ai + bj + ck
> V2 = di + ej + fk
> 
> then the cross product is
>   V1 x V2    =  (bf - ce) i + (cd - af) j + (ae - bd) k
> 
> 
> As shown here ( http://en.wikipedia.org/wiki/Cross_product ).
> 
> Thanks.
> 
> Best,
> Bai
> 
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-- 
Eik Vettorazzi
Institut für Medizinische Biometrie und Epidemiologie
Universitätsklinikum Hamburg-Eppendorf

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