[R] labeled break statements in R?

Gabor Grothendieck ggrothendieck at myway.com
Thu Aug 19 06:13:15 CEST 2004

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)
	for(i in 1:3) 
		for(j in 1:3)
			if (i+j>4) return() else a[i,j] <<- i+j

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)

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