[R] question regarding vector ops

[Rajarshi Guha]

On Fri, 2004-04-09 at 12:03, Rajarshi Guha wrote:
> Hi,
>   I was playing with some code and came upon this situation.
> 
> > x <- c(1, rep(0,9))
> > x
>  [1] 1 0 0 0 0 0 0 0 0 0
> > idx <- 1:10
> > x[idx] <- x[idx] + 1
> > x
>  [1] 2 1 1 1 1 1 1 1 1 1
> 
> This is expected. But if I do:
> 
> > x <- c(1, rep(0,9))
> > x
>  [1] 1 0 0 0 0 0 0 0 0 0
> > idx <- rep(0,10)
> > idx
>  [1] 0 0 0 0 0 0 0 0 0 0
> > x[idx] <- x[idx] +1
> > x
>  [1] 1 0 0 0 0 0 0 0 0 0

Aah, I realize that the second code snippet is not supposed to work.
What I meant was:

> x <- c(1, rep(0,9))
> x
 [1] 1 0 0 0 0 0 0 0 0 0
> idx <- rep(1,10)
>idx
 [1] 1 1 1 1 1 1 1 1 1 1
> x[idx] <- x[idx] + 1
 [1] 2 0 0 0 0 0 0 0 0 0

I expected that x would be

[1] 11 0 0 0 0 0 0 0 0 0

Or am I thinking about it wrong?

Thanks,

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Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net>
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