[R] vectorization help please

Uwe Ligges ligges at statistik.uni-dortmund.de
Wed Sep 26 11:20:48 CEST 2001



Bill Simpson wrote:
> 
> What is a smarter way of doing:
> 
> for(i in 1:xn)
> for(j in 1:yn)
> {
> im2[i,j]<- im[i,j]* (-1)^(i+j)
> }


 im * (-1)^(row(im) + col(im))

Uwe
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