A **`while` loop** is a block of code that can be repeatedly executed given the condition needed to execute it, returns `true`. Hence, the code runs in a loop as long as the condition holds.

# Understanding the `while` loop

The first step to writing a loop is to understand the logic behind it. The illustration below shows the workings of a `while` loop:


# Syntax

The next step is to understand the syntax of a `while` loop in R. The code snippet below shows how to code a `while` loop in R.

The **`condition_statement`** is a single condition or a set of multiple conditions that return a boolean value of `true` or `false`. 

If the returned value is `true` only then will the loop execute the code inside it. 

while(condition_statement){
  #Loop body goes here
}

# Examples

Now that we know how a `while` loop works and its syntax, let's look at a few examples to better understand how to use it in R. 

## 1. Will the loop even execute?

This example shows what happens when the condition statement is `false` from the start. The code inside the loop body is not executed and the program moves on to the code outside the while block.

iterator <- 10
while(iterator>11){
  print("In while loop")
  iterator <- iterator + 1
}

print("Outside while loop")


## 2. Using a single condition

This `while` loop, in the example below, has a condition statement based on an incrementing numeric value. When the value of the `iterator` exceeds 10, it should break.

iterator <- 1
while(iterator<=10){
  print(iterator)
  iterator <- iterator + 1
}

print("Outside while loop")


## 3. Using multiple conditions

This example shows how to use more than one condition in the loop. As seen on *line 4* the `while` loop has two conditions, one using the `AND` operator and the other using the `OR`operator.

>**Note:** The `AND` condition must be fulfilled for the loop to run. However, if either of the conditions on the `OR` side of the operator returns `true`, the loop will run.


iterator <- 1
second_iterator <- 10
third_iterator <-1
while(third_iterator <=4 && iterator<=10 || second_iterator<5){
  cat("First Iterator: ", iterator, "\n")
  cat("Second iterator: ",second_iterator, "\n")
  cat("Third iterator: ",third_iterator, "\n")
  iterator <- iterator + 1
  second_iterator <- second_iterator + 1
  third_iterator <- third_iterator + 1
}

print("Outside while loop")


How to use a while loop in R

A while loop in R repeatedly executes code while its condition is true. Syntax and examples demonstrate single and multiple conditions.

How to use a while loop in R

Understanding the while loop

Syntax

Examples

1. Will the loop even execute?

2. Using a single condition

3. Using multiple conditions

Understanding the `while` loop