R while Loop

Introduction

In this chapter, you will learn about the while loop in R. The while loop is a control structure that allows you to repeatedly execute a block of code as long as a specified condition is TRUE. Understanding how to use the while loop is essential for performing tasks that require repeated execution based on a condition.

The while Loop

Basic Usage

The while loop in R continues to execute a block of code as long as the specified condition remains TRUE. If the condition becomes FALSE, the loop stops.

Syntax

while (condition) {
  # Code to execute while the condition is TRUE
}

• condition: A logical expression that is evaluated before each iteration. If it evaluates to TRUE, the loop continues; if it evaluates to FALSE, the loop stops.

Examples

Example 1: Basic while Loop

In this example, the while loop prints numbers from 1 to 5.

Example:

# Basic while loop
i <- 1

while (i <= 5) {
  print(i)
  i <- i + 1
}
# Output:
# [1] 1
# [1] 2
# [1] 3
# [1] 4
# [1] 5

Example 2: Summing Numbers Using while Loop

In this example, the while loop calculates the sum of numbers from 1 to 10.

Example:

# Summing numbers using while loop
sum <- 0
i <- 1

while (i <= 10) {
  sum <- sum + i
  i <- i + 1
}

print(paste("The sum is:", sum))
# Output: [1] "The sum is: 55"

Example 3: Using break in a while Loop

In this example, the break statement is used to exit the loop when a specific condition is met.

Example:

# Using break in a while loop
i <- 1

while (TRUE) {
  if (i > 5) {
    break  # Exit the loop
  }
  print(i)
  i <- i + 1
}
# Output:
# [1] 1
# [1] 2
# [1] 3
# [1] 4
# [1] 5

Example 4: Using next in a while Loop

In this example, the next statement is used to skip the current iteration when a specific condition is met.

Example:

# Using next in a while loop
i <- 1

while (i <= 10) {
  i <- i + 1
  if (i %% 2 == 0) {
    next  # Skip even numbers
  }
  print(i)
}
# Output:
# [1] 3
# [1] 5
# [1] 7
# [1] 9
# [1] 11

Example Program with while Loop

Here is an example program that demonstrates the use of the while loop in R:

# R Program to Demonstrate while Loop

# Using while loop to calculate factorial of a number
factorial <- function(n) {
  result <- 1
  i <- 1

  while (i <= n) {
    result <- result * i
    i <- i + 1
  }

  return(result)
}

# Calculate factorial of 5
n <- 5
fact <- factorial(n)

# Print the factorial
print(paste("The factorial of", n, "is:", fact))
# Output: [1] "The factorial of 5 is: 120"

# Using while loop to find the first number greater than 100 that is divisible by 7
num <- 1

while (TRUE) {
  if (num > 100 && num %% 7 == 0) {
    print(paste("The first number greater than 100 that is divisible by 7 is:", num))
    break
  }
  num <- num + 1
}
# Output: [1] "The first number greater than 100 that is divisible by 7 is: 105"

Conclusion

In this chapter, you learned about the while loop in R, including how to use it for basic iteration, summing numbers, and more complex tasks like calculating factorials and finding specific numbers. You also learned how to incorporate the break and next statements within a while loop. The while loop is used for performing tasks that require repeated execution based on a condition. By mastering the while loop, you can write more dynamic and efficient R programs.