[R] any alternatives for complex for-loops?

[David Winsemius]

y <- rep(NA, length(x))
a <- 2:length(x)
y[a] <- complexFn( x[a-1], x[a] )

 >  y
  [1]  NA 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5

-- 
David Winsemius

On Nov 12, 2008, at 12:48 AM, Kinoko wrote:

> Thanks for the replies
>
> Sorry for being unclear.
>
> I am asking if there is a way to process a vector in a way
> that uses references to other elements of the same vector.
> And doing this without a for-loop.
>
> Here is a running code:
>
> <code>
> complexFn <- function(a,b){
>  c <- (a+b)/2
>  return(c)
> }
>
> x <- 1:10
> y <- rep(NA, length(x))
>
> for (i in 1:length(x)){
>    if(i>1){
>        y[i] = complexFn(x[i-1], x[i])
>    }
> }
> print(y)
> </code>
>
> And here is another attempt without the for-loop.
>
> <code>
> x <- 1:10
> x1 <- c(NA, x)
> length(x1)<-length(x)
>
> y<-mapply(complexFn,x,x1)
> print(c(y))
> </code>
>
> If someone could tell me the normal/elegant/effective/R way of
> doing this kind of vector processing, that would highly appreciated.
>
> best,
>
> gabor
>
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