For loop in R Programming

Introduction

A for loop helps you repeat a set of actions many times without writing the same code again and again.

When you want to print numbers from 1 to 10.

When you need to add up all values in a list.

When you want to apply the same change to each item in a group.

When you want to check each element in a collection one by one.

Syntax

R Programming

for (variable in sequence) {
  # code to repeat
}

The variable takes each value from the sequence one by one.

The code inside the curly braces { } runs for each value.

Examples

Prints numbers 1 to 5, one by one.

R Programming

for (i in 1:5) {
  print(i)
}

Prints each letter in the list.

R Programming

for (letter in c('a', 'b', 'c')) {
  print(letter)
}

Prints even numbers from 2 to 10.

R Programming

for (num in seq(2, 10, by=2)) {
  print(num)
}

Sample Program

This program goes through numbers 1 to 4, calculates their squares, and prints the result.

R Programming

numbers <- 1:4
for (n in numbers) {
  square <- n^2
  print(paste(n, "squared is", square))
}

Important Notes

Make sure the sequence you use in the for loop is not empty, or the loop will not run.

Indent the code inside the loop to keep it clear and easy to read.

Summary

A for loop repeats actions for each item in a sequence.

Use it to avoid writing repetitive code.

The loop variable changes automatically with each repetition.