## Introduction

In this chapter, you will learn about the `for`

loop in R. The `for`

loop is a fundamental control structure that allows you to iterate over a sequence of elements and execute a block of code for each element. Understanding how to use the `for`

loop is essential for performing repetitive tasks and automating processes in your R programs.

## The for Loop

### Basic Usage

The `for`

loop in R iterates over a sequence (such as a vector, list, or other iterable objects) and executes a block of code for each element in the sequence.

### Syntax

```
for (variable in sequence) {
# Code to execute for each element in the sequence
}
```

`variable`

: A variable that takes the value of each element in the sequence.`sequence`

: A sequence of elements to iterate over.

### Example 1: Iterating Over a Vector

In this example, the `for`

loop iterates over a vector and prints each element.

**Example**:

```
# Iterating over a vector
numbers <- c(1, 2, 3, 4, 5)
for (num in numbers) {
print(num)
}
# Output:
# [1] 1
# [1] 2
# [1] 3
# [1] 4
# [1] 5
```

### Example 2: Using a for Loop with a Sequence

In this example, the `for`

loop iterates over a sequence of numbers generated by the `1:10`

expression.

**Example**:

```
# Using a for loop with a sequence
for (i in 1:10) {
print(i)
}
# Output:
# [1] 1
# [1] 2
# [1] 3
# [1] 4
# [1] 5
# [1] 6
# [1] 7
# [1] 8
# [1] 9
# [1] 10
```

### Example 3: Iterating Over a List

In this example, the `for`

loop iterates over a list and prints each element.

**Example**:

```
# Iterating over a list
my_list <- list("apple", "banana", "cherry")
for (fruit in my_list) {
print(fruit)
}
# Output:
# [1] "apple"
# [1] "banana"
# [1] "cherry"
```

### Example 4: Nested for Loops

In this example, nested `for`

loops are used to iterate over a matrix and print each element.

**Example**:

```
# Nested for loops
matrix_data <- matrix(1:9, nrow = 3, ncol = 3)
for (i in 1:nrow(matrix_data)) {
for (j in 1:ncol(matrix_data)) {
print(matrix_data[i, j])
}
}
# Output:
# [1] 1
# [1] 2
# [1] 3
# [1] 4
# [1] 5
# [1] 6
# [1] 7
# [1] 8
# [1] 9
```

### Example 5: Using the break Statement

In this example, the `break`

statement is used to exit the loop when a condition is met.

**Example**:

```
# Using the break statement
for (i in 1:10) {
if (i == 5) {
break # Exit the loop
}
print(i)
}
# Output:
# [1] 1
# [1] 2
# [1] 3
# [1] 4
```

### Example 6: Using the next Statement

In this example, the `next`

statement is used to skip the current iteration when a condition is met.

**Example**:

```
# Using the next statement
for (i in 1:10) {
if (i %% 2 == 0) {
next # Skip even numbers
}
print(i)
}
# Output:
# [1] 1
# [1] 3
# [1] 5
# [1] 7
# [1] 9
```

## Example Program with for Loop

Here is an example program that demonstrates the use of the `for`

loop in R:

```
# R Program to Demonstrate for Loop
# Declare a vector of numbers
numbers <- c(10, 20, 30, 40, 50)
# Calculate the sum of the numbers using a for loop
sum <- 0
for (num in numbers) {
sum <- sum + num
}
# Print the sum
print(paste("The sum of the numbers is:", sum))
# Output: [1] "The sum of the numbers is: 150"
# Using a for loop to create a multiplication table
multiplication_table <- function(n) {
for (i in 1:10) {
result <- n * i
print(paste(n, "x", i, "=", result))
}
}
# Create a multiplication table for 5
multiplication_table(5)
# Output:
# [1] "5 x 1 = 5"
# [1] "5 x 2 = 10"
# [1] "5 x 3 = 15"
# [1] "5 x 4 = 20"
# [1] "5 x 5 = 25"
# [1] "5 x 6 = 30"
# [1] "5 x 7 = 35"
# [1] "5 x 8 = 40"
# [1] "5 x 9 = 45"
# [1] "5 x 10 = 50"
```

## Conclusion

In this chapter, you learned about the `for`

loop in R, including how to iterate over vectors, lists, sequences, and matrices. You also learned how to use nested `for`

loops, and how to incorporate the `break`

and `next`

statements within a `for`

loop. The `for`

loop is used for performing repetitive tasks and automating processes in your R programs. By mastering the `for`

loop, you can write more efficient and flexible R code.