R – while loop

While loop in R programming language is used when the exact number of iterations of loop is not known beforehand. It executes the same code again and again until a stop condition is met. While loop checks for the condition to be true or false n+1 times rather than n times. This is because the while loop checks for the condition before entering the body of the loop.

R- While loop Syntax:

while (test_expression) {
   statement
   update_expression
}  

How does a While loop execute?

• Control falls into the while loop.
• The flow jumps to Condition
• Condition is tested. 
  • If Condition yields true, the flow goes into the Body.
  • If Condition yields false, the flow goes outside the loop
• The statements inside the body of the loop get executed.
• Updation takes place.
• Control flows back to Step 2.
• The while loop has ended and the flow has gone outside.

Important Points about while loop in R language:

• It seems to be that while loop will run forever but it is not true, condition is provided to stop it.
• When the condition is tested and the result is false then loop is terminated.
• And when the tested result is True, then loop will continue its execution.

R – while loop Flowchart:

While Loop in R Programming Examples

Example 1:

R

# R program to illustrate while loop

result <- c("Hello World")
i <- 1

# test expression
while (i < 6) {

   print(result)

   # update expression
   i = i + 1
}

Output:

[1] "Hello World"
[1] "Hello World"
[1] "Hello World"
[1] "Hello World"
[1] "Hello World"

Example 2:

R

# R program to illustrate while loop

result <- 1
i <- 1

# test expression
while (i < 6) {

   print(result)

   # update expression
   i = i + 1
   result = result + 1
}

Output:

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

R – while loop break

Here we will use the break statement in the R programming language. Break statement in R is used to bring the control out of the loop when some external condition is triggered.

R

# R program to illustrate while loop

result <- c("Hello World")
i <- 1

# test expression
while (i < 6) {

    print(result)

    if( i == 3){
        break}
    # update expression
    i = i + 1
}

Output:

[1] "Hello World"
[1] "Hello World"
[1] "Hello World"