[R] labeled break statements in R?

[Gabor Grothendieck]

Gabor Grothendieck <ggrothendieck <at> myway.com> writes:

: 
: Roger Levy <rog <at> stanford.edu> writes:
: 
: : 
: : Hi,
: : 
: : Are there labeled break statements in R?  i.e., something along the
: : lines of
: : 
: : TOPLOOP: for(i in 1:m) {
: :   for(j in 1:n) {
: :     ...
: :     if(condition) {
: :        break TOPLOOP
: :     }
: :   }
: : }
: 
: Assuming that your labelled break is supposed to break out of
: both loops, unlike an ordinary break that just breaks out of
: the inner loop, this is how it would be done:
: 
: a <- matrix(0, nr=3, nc=3)
: local({
: 	for(i in 1:3) 
: 		for(j in 1:3)
: 			if (i+j>4) return() else a[i,j] <<- i+j
: })
: a
: 
: Be aware that assigning variables within the local will assign
: local copies unless you use <<-, assign(..., ..., parent.frame())
: or eval.parent(...).
: 
: Of course this style is not recommended for R, and as someone else 
: already mentioned, you should try to vectorize your code eliminating 
: the loops altogether.  For example, the above could be written 
: without loops like this:
: 
: a <- matrix(0, nr=3, nc=3)
: rc <- row(a) + col(a)
: a <- ifelse(rc > 4, a, rc)
: a
: 
Sorry, the ifelse line should have been:

ifelse( t(matrix(cumsum(rc>4),3,3)), a, rc)