R – while loop
Last Updated :
10 May, 2023
While loop in R programming language is used when the exact number of iterations of a 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 the Condition yields true, the flow goes into the Body.
- If the 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 the 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 the loop is terminated.
- And when the tested result is True, then the loop will continue its execution.
R – while loop Flowchart:
R – while loop
While Loop in R Programming Examples
Example 1:
R
result <- c("Hello World")
i <- 1
while (i < 6) {
print(result)
i = i + 1
}
|
Output:
[1] "Hello World"
[1] "Hello World"
[1] "Hello World"
[1] "Hello World"
[1] "Hello World"
Example 2:
R
result <- 1
i <- 1
while (i < 6) {
print(result)
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. The break statement in R is used to bring the control out of the loop when some external condition is triggered.
R
result <- c("Hello World")
i <- 1
while (i < 6) {
print(result)
if( i == 3){
break}
i = i + 1
}
|
Output:
[1] "Hello World"
[1] "Hello World"
[1] "Hello World"
R – while loop next
R
x <- 1
while (x < 10) {
if (x == 3) {
x <- x + 1
next
}
print(paste("The current value of x is:", x))
x <- x + 1
}
print("The loop has ended.")
|
Output
[1] "The current value of x is: 1"
[1] "The current value of x is: 2"
[1] "The current value of x is: 4"
[1] "The current value of x is: 5"
[1] "The current value of x is: 6"
[1] "The current value of x is: 7"
[1] "The current value of x is: 8"
[1] "The current value of x is: 9"
In this instance, x’s initial value is set to 1 at the beginning. Then, as long as x is less than 10, we continue iterating using a while-loop. We use an if statement inside the loop to see if x equals 3. If so, the loop’s current iteration is skipped in favor of the following one using the next statement. If not, we use the x – x + 1 expression to increment x by 1 and output a message stating the current value of x.
The next line instructs R to move on to the next iteration of the loop and skip the current one. based on a condition, over a subset of the loop’s iterations without ever leaving the loop.
R While Loop with If .. Else
R
x <- 1
while (x <= 10) {
if (x %% 2 == 0) {
print(paste(x, "is even"))
} else {
print(paste(x, "is odd"))
}
x <- x + 1
}
|
Output
[1] "1 is odd"
[1] "2 is even"
[1] "3 is odd"
[1] "4 is even"
[1] "5 is odd"
[1] "6 is even"
[1] "7 is odd"
[1] "8 is even"
[1] "9 is odd"
[1] "10 is even"
In this illustration, we initialize a variable x to 1, and then we iterate through the integers 1 through 10 using a while loop. We utilize an if-else statement inside the loop to determine whether x is even or odd. We publish a message stating that x is even if it is. We print a message noting that x is unusual if it is. Then, until x is more than 10, we increase x by 1 and loop till x is greater than 10.
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