R: How to decrease counter in for loop

Question

I would like to do 10 iterations, but sometimes flag is bigger that 1. In this case I must to decrease variable i by 1 and calculate flag again. How to do this decrement?

    for(i in (1:n)){ 
    flag <- ... # some code
        if (flag > 1) {
         # some code
        } 
        #else decrement i <- i - 1 ??
    }

Thanks.

@yeouuu thanks for reply. Language is "R". else {i--} does not work. — Nick, Dec 29 '15 at 14:28
for the record to have a true decreasing for loop simply change `1:n` to `n:1`. — MichaelChirico, Dec 29 '15 at 14:32

score 6 · Answer 1 · answered Dec 29 '15 at 14:21

6

That's what a while loop is for, not for loop.

i <- 1
while(i <= 10)
{
  i <- i + 1 #
  flag <- ... # some code
  if (flag > 1) {
    # some code
  } 
  else{
    i <- #some arbitrary number    
  }
}

Do note however that you may end up in infinite loop if you are not careful.

answered Dec 29 '15 at 14:21

Jakub Kania

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1

`i <- #some arbitrary number` should be probably `i <- i - 1` to make this clearer. – David Arenburg Dec 29 '15 at 14:27
@DavidArenburg If that was i - 1 it would be much better to do a `continue` before incrementing the flag. – Jakub Kania Dec 29 '15 at 14:31
@DavidArenburg But yeah, you're right. I'd be happy to clarify it if OP clarifies his question. – Jakub Kania Dec 29 '15 at 14:35

R: How to decrease counter in for loop

1 Answers1