R help - Mar 2015 - Looping and break

Hello,

I apologies for bringing up next and break in loops given that there is so
much on the net about it, but I've tried numerous examples found using
Google and just can't seem to get this to work.

This is a simple version of what I am doing with matrices but it shows the
issue. I need to have the loop indexed as n to perform a calculation on the
variable total. But if "total" is greater than 8, it goes to the next
loop
indexed "a".  For example, it does condition a = 1 for n = 1 to 50 but
within n if total is greater than 8 it goes to the next condition of a which
would be a = 2, and so on.

for (a in 1:3){
  
  if (a == 1) { b <- c(1:5) }
  if (a == 2) { b <- c(1:5) }
  if (a == 3) { b <- c(1:5) }
  
  for (n in 1:50){
  
     if (n > 15) next
    
     total <- 2*b
  
     if (total > 8) next
    
  }
}

Any help would be greatly appreciated.

Thanks,

Scott



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Your example is decidedly not expressed in R, though it looks like you tried.
Can you provide the hand-computed result that you are trying to obtain?

Note that the reason you cannot find anything about next or break in R is that
they don't exist. There are generally alternative ways to accomplish the
kinds of things you might want to accomplish without them, and those
alternatives often don't involve explicit loops at all.
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On March 2, 2015 4:11:21 PM PST, Scott Colwell <scolwell at uoguelph.ca>
wrote:
>Hello,
>
>I apologies for bringing up next and break in loops given that there is
>so
>much on the net about it, but I've tried numerous examples found using
>Google and just can't seem to get this to work.
>
>This is a simple version of what I am doing with matrices but it shows
>the
>issue. I need to have the loop indexed as n to perform a calculation on
>the
>variable total. But if "total" is greater than 8, it goes to the
next
>loop
>indexed "a".  For example, it does condition a = 1 for n = 1 to 50
but
>within n if total is greater than 8 it goes to the next condition of a
>which
>would be a = 2, and so on.
>
>for (a in 1:3){
>  
>  if (a == 1) { b <- c(1:5) }
>  if (a == 2) { b <- c(1:5) }
>  if (a == 3) { b <- c(1:5) }
>  
>  for (n in 1:50){
>  
>     if (n > 15) next
>    
>     total <- 2*b
>  
>     if (total > 8) next
>    
>  }
>}
>
>Any help would be greatly appreciated.
>
>Thanks,
>
>Scott
>
>
>
>--
>View this message in context:
>http://r.789695.n4.nabble.com/Looping-and-break-tp4704093.html
>Sent from the R help mailing list archive at Nabble.com.
>
>______________________________________________
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

On 03/03/15 15:04, Jeff Newmiller wrote:
> Your example is decidedly not expressed in R, though it looks like
> you tried. Can you provide the hand-computed result that you are
> trying to obtain?
>
> Note that the reason you cannot find anything about next or break in
> R is that they don't exist.
Point of order, Mr. Chairman, but they ***do*** exist.  See e.g
?"next"
(which actually takes you to the help for "Control Flow").
> There are generally alternative ways to
> accomplish the kinds of things you might want to accomplish without
> them, and those alternatives often don't involve explicit loops at
> all.
Otherwise I concur with everything you say.

cheers,

Rolf

-- 
Rolf Turner
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276
Home phone: +64-9-480-4619