[R] vectorization help please

[Anders Nielsen]

How about? 

 im2<-im*(2*(1:length(im)%%2)-1)

Anders 


On Wed, 26 Sep 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)
> }
> 
> Thanks!
> 
> Bill
> 
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