[R] R question

Ross Ihaka ihaka at stat.auckland.ac.nz
Thu Dec 16 19:49:17 CET 1999

On Thu, Dec 16, 1999 at 02:41:25PM -0500, Faheem Mitha wrote:
> I have the following question, which is elementary but I am unable to
> answer.
> In a for(i=10) loop, I am trying to represent the 10 1-dimensional vectors 
> l1, l2,... l10 by some expression that will run through these values.
> ie. soppose I want to add l1 + ... + l10
> I could go
> x <- 0
> for(i in 1:10){ x <- x+ l(i)} 
> This should return x to be the sum of the 10 li's for i from 1 to 10
> except of course I'm doing something more complicated. 
> But l(i) of course does not serve to represent l1 etc? What should I do?

Subsetting in S (and hence R) uses [] for subsetting.  What you need is

	x <- 0
	for(i in 1:10) x <- x + l[i]

(If the values are really in a vector, x <- sum(l) is rather faster).

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