In R programming, a normal looping sequence can be altered using the
break or the next statement.
break statement
A break statement is used inside a loop (repeat, for,
while) to stop
the iterations and flow the control outside of the loop.
In a nested looping situation, where there is a loop inside another loop, this statement exits from the innermost loop that is being evaluated.
The syntax of break statement is:
if (test_expression) {
break
}
Note: the break statement can also be used inside the else
branch of if...else statement.
Flowchart of break statement
Example 1: break statement
x <- 1:5
for (val in x) {
if (val == 3){
break
}
print(val)
}
Output
[1] 1 [1] 2
In this example, we iterate over the vector x, which has
consecutive numbers from 1 to 5.
Inside the for loop we have used a if condition to break if the current value is equal to 3.
As we can see from the output, the loop terminates when it encounters the
break statement.
next statement
A next statement is useful when we want to skip the current iteration of a
loop without terminating it. On encountering next, the R parser
skips further evaluation and starts next iteration of the loop.
The syntax of next statement is:
if (test_condition) {
next
}
Note: the next statement can also be used inside else
branch of if...else statement.
Flowchart of next statement
Example 2: Next statement
x <- 1:5
for (val in x) {
if (val == 3){
next
}
print(val)
}
Output
[1] 1 [1] 2 [1] 4 [1] 5
In the above example, we use the next statement inside a
condition to check if the value is equal to 3.
If the value is equal to 3, the current evaluation stops (value is not printed) but the loop continues with the next iteration.
The output reflects this situation.