[R] behavior of seq_along

[David Winsemius]

On Feb 25, 2010, at 9:02 AM, Dale Steele wrote:

> I'm trying to understand the behavior of seq_along in the following  
> example:
>
> x <- 1:5; sum(x)
> y <- 6:10; sum(y)
>
> data <- c(x,y)
> S <- sum( data[seq_along(x)] )
> S
> T <- sum( data[seq_along(y)] )
> T
>
> Why is T != sum(y) ?

Look at

seq_along(y)

seq_along returns indices for the purpose of accession of elements, so  
it starts with 1 and ends with the length of the object.

Had you asked for sum(data[y[seq_along(y)]]) you might have achieved  
your expectation.

>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT