Iterative Statements in R

June 04, 2026

Iterative Statements in R

Introduction

Iterative statements, also known as looping statements, are used to repeatedly execute a block of code until a specified condition is satisfied. Loops eliminate the need to write the same statements multiple times and make programs more compact and efficient.

R provides three looping constructs:

for Loop
while Loop
repeat Loop

R also provides two loop control statements:

break Statement
next Statement

1. for Loop

Definition

The for loop is used to execute a block of code repeatedly for each value in a sequence, vector, list, or other iterable object.

Syntax


for(variable in sequence)
{
    statements
}

where:

variable represents the loop variable.
sequence specifies the values over which the loop iterates.
statements are executed once for each value in the sequence.

Flowchart


          Sequence
              |
        Assign next value
              |
         Execute statements
              |
       More values available?
          Yes       No
           |         |
          Repeat    Stop

Example 1: Print Numbers from 1 to 5


for(i in 1:5)
{
    print(i)
}

Output


[1] 1
[1] 2
[1] 3
[1] 4
[1] 5

Example 2: Find Squares of Numbers


for(i in 1:5)
{
    print(i^2)
}

Output


[1] 1
[1] 4
[1] 9
[1] 16
[1] 25

Applications

Printing tables.
Processing vectors and matrices.
Repeating operations a fixed number of times.

2. while Loop

Definition

The while loop repeatedly executes a block of code as long as a specified condition remains TRUE.

Syntax


while(condition)
{
    statements
}

Flowchart


        Condition
            |
       +----+----+
       |         |
     TRUE      FALSE
       |         |
 Execute      Stop
 statements
       |
   Repeat

Example 1: Print Numbers from 1 to 5


i <- 1

while(i <= 5)
{
    print(i)
    i <- i + 1
}

Output


[1] 1
[1] 2
[1] 3
[1] 4
[1] 5

Example 2: Sum of First Five Natural Numbers


i <- 1
sum <- 0

while(i <= 5)
{
    sum <- sum + i
    i <- i + 1
}

print(sum)

Output


[1] 15

Applications

Unknown number of iterations.
Reading data until a condition is met.
Menu-driven programs.

3. repeat Loop

Definition

The repeat loop repeatedly executes a block of code indefinitely. The loop terminates only when a break statement is encountered.

Syntax


repeat
{
    statements

    if(condition)
        break
}

Flowchart


       Execute statements
               |
         Termination condition?
          Yes            No
           |              |
         break          Repeat

Example 1: Print Numbers from 1 to 5


i <- 1

repeat
{
    print(i)

    i <- i + 1

    if(i > 5)
        break
}

Output


[1] 1
[1] 2
[1] 3
[1] 4
[1] 5

Example 2: Sum of Natural Numbers


i <- 1
sum <- 0

repeat
{
    sum <- sum + i
    i <- i + 1

    if(i > 5)
        break
}

print(sum)

Output


[1] 15

4. break Statement

Definition

The break statement is used to terminate a loop immediately. Control passes to the statement following the loop.

Syntax


break

Example 1: Using break in a for Loop


for(i in 1:10)
{
    if(i == 6)
        break

    print(i)
}

Output


[1] 1
[1] 2
[1] 3
[1] 4
[1] 5

The loop terminates when i becomes 6.

Example 2: Using break in a while Loop


i <- 1

while(TRUE)
{
    print(i)

    if(i == 5)
        break

    i <- i + 1
}

Output


[1] 1
[1] 2
[1] 3
[1] 4
[1] 5

Applications of break

Exiting loops prematurely.
Stopping infinite loops.
Terminating loops when a desired condition is achieved.

5. next Statement

Definition

The next statement skips the remaining statements in the current iteration and proceeds to the next iteration of the loop.

Syntax


next

Example 1: Skip Number 5


for(i in 1:10)
{
    if(i == 5)
        next

    print(i)
}

Output


[1] 1
[1] 2
[1] 3
[1] 4
[1] 6
[1] 7
[1] 8
[1] 9
[1] 10

Number 5 is skipped.

Example 2: Print Odd Numbers Only


for(i in 1:10)
{
    if(i %% 2 == 0)
        next

    print(i)
}

Output


[1] 1
[1] 3
[1] 5
[1] 7
[1] 9

Applications of next

Skipping unwanted values.
Ignoring invalid data.
Filtering elements during iteration.

Comparison of Looping Statements

Feature	for	while	repeat
Number of iterations known beforehand	Yes	No	No
Condition checked before execution	Implicit	Yes	No
Infinite loop possible	No	Yes	Yes
Requires break to terminate	No	No	Yes

Comparison of break and next

Statement	Effect
`break`	Terminates the loop completely
`next`	Skips the current iteration and continues with the next iteration

Summary

Statement	Purpose
`for`	Repeat statements over a sequence
`while`	Repeat while a condition remains TRUE
`repeat`	Infinite loop until terminated by `break`
`break`	Exit the loop immediately
`next`	Skip the current iteration

Conclusion

Looping statements in R provide mechanisms for executing a block of code repeatedly. The for loop is suitable when the number of iterations is known, the while loop is useful when repetition depends on a condition, and the repeat loop supports indefinite repetition until explicitly terminated. The break statement terminates a loop, whereas the next statement skips the current iteration and continues with the next one. These constructs are essential for developing efficient and flexible R programs.