R Break and Next

Stopping a loop early with break

Normally a loop runs until its condition is false (while) or its sequence is exhausted (for). break interrupts that early: as soon as R executes break, it exits the loop immediately, skipping any remaining iterations, and continues with the code after the loop.

numbers <- c(4, 9, 15, 22, 7, 3)
for (n in numbers) {
  if (n %% 2 != 0) {
    cat("Found the first odd number:", n, "\n")
    break
  }
}

Skipping an iteration with next

next works differently: it doesn't end the loop, it just ends the current pass through the body early and jumps straight to the next iteration, re-checking the loop's condition or moving to the next element of the sequence.

for (n in 1:10) {
  if (n %% 2 == 0) {
    next
  }
  cat(n, "is odd\n")
}

Using break and next together

total <- 0
for (n in c(5, -2, 8, -1, 12, 40)) {
  if (n < 0) {
    next
  }
  total <- total + n
  if (total > 20) {
    break
  }
}
cat("Final total:", total, "\n")

• Stop searching as soon as a match is found (break)
• Skip invalid or unwanted values while keeping the loop going (next)
• End a loop once a running total or counter passes a limit (break)
• Filter out certain cases without writing a large nested if-else (next)

Used sparingly, break and next can make loops easier to read than deeply nested if statements, because they let you handle special cases up front and keep the main logic of the loop uncluttered.