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Exploring Control Structures in R Programming: Learn How to Use While Loops and Statements Like Repeat, Break, Continue, Next and Return to Enhance Your Code!

The Beginner’s Guide to Control Structures (While Loops, Repeat, Break, Continue, Next and Return) in R Programming:

Control structures are an essential aspect of programming in any language, including R. In R, control structures help programmers to define the flow of a program's logic. In addition to if-else statements, switch cases, and for loops, R also supports while loops and statements such as repeat, break, continue, next, and return. This blog post will explain how to use these control structures in R and provide practice material for learners.


While Loop:

The while loop is used to execute a block of code repeatedly as long as the specified condition remains true. The syntax of the while loop in R is as follows:

while (condition) {
  # Execute code as long as the condition is true
}

For example, consider the following code that prints the numbers from 1 to 5 using a while loop:

i <- 1

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

Output:
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5

Repeat, Break, Continue, Next and Return statements:

The repeat statement is used to execute a block of code repeatedly until a specified condition is met. The syntax of the repeat statement in R is as follows:

repeat {
  # Execute code repeatedly
  if (condition) {
    break # Exit the loop if the condition is true
  }
}

The break statement is used to exit a loop prematurely if a specified condition is met. The syntax of the break statement in R is as follows:

for (i in 1:5) {
  if (i == 3) {
    break # Exit the loop if i is equal to 3
  }
  print(i)
}

The continue statement is used to skip the current iteration of a loop and move on to the next iteration. The syntax of the continue statement in R is as follows:

for (i in 1:5) {
  if (i == 3) {
    continue # Skip the iteration if i is equal to 3
  }
  print(i)
}

The return statement is used to exit a function and return a value. The syntax of the return statement in R is as follows:

my_function <- function(x, y) {
  if (x == y) {
    return("x is equal to y")
  }
  return("x is not equal to y")
}

The next statement in R is used to skip the current iteration of a loop and move on to the next iteration. This statement is typically used in for loops, while loops, and repeat loops to skip over certain iterations based on a specified condition. For example, consider the following code that uses a for loop to print all even numbers from 1 to 10:

for (i in 1:10) {
  if (i %% 2 != 0) {
    next # Skip the iteration if i is odd
  }
  print(i)
}

Output:
[1] 2
[1] 4
[1] 6
[1] 8
[1] 10

In this code, the modulo operator (%%) is used to determine if a number is even or odd. If the number is odd, the next statement is used to skip the current iteration of the loop and move on to the next iteration. As a result, only even numbers are printed to the console.

Practice Material:

Here are a few practice exercises to help you get started:

  • Write a program that calculates the sum of the first 10 natural numbers using a while loop.
  • Write a program that takes a list of numbers as input and returns the sum of all even numbers in the list. Use a repeat loop to prompt the user to enter a number until they enter -1 to break the loop. Use a continue statement to skip odd numbers in the loop.
  • For more practice you should start swirl's lessons in  R Programming. Complete download process of swirl and R Programming is here, click on the link!
  • You can look in to the practice and reading material that is provided in the text book, click here to download the textbook.
  • Lecture slides can be downloaded from here. It would be great if you go through them too.

These practice materials are suitable for you to get hands-on experience with while loops and repeat, break, continue, next, and return statements in R programming. Good luck with your learning!
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