#     
## Introduction

The **`if`** statement in R executes a single block of statements based on a logical expression.

The syntax is as follows:
```R
if (expression) {
  statement
}
```
The `expression` in the code is usually a boolean expression (`true` or `false`). The program above will only execute the provided `statement` if the `expression` is `true`.

## Code

Let's write a simple code to illustrate the `if` statement.


x <- 1
y <- 2

if (y > x){
  print("y is greater than x")
}

In the code above, we can see that the `expression` is `true`, so the `statement` is executed.

An `if` statement can also come with an `else` block; this is called an **`if-else`** statement.

#    
## The `if-else` statement
The **`if-else`** statement has two blocks of statements and executes one of them based on certain logical expressions.

The syntax is as follows:
```R
if (expression){
    statement_1(s)
    ---
}else{
    statement_2(s)
}
```
The code above will only execute the `if` block if the `expression` is `true`. If the `expression` is `false`, then the program executes `statement_2` in the `else` block.

## Code

x <- 1
y <- 2

if (y < x){
  print("y is less than x")
}else{
    print("x is less than y")
}

In the code above, the value of `x` is less than that of `y`, so the first condition is not `true`. The `else` condition tells us that if otherwise (i.e. the expression is not `true`), it should return another statement from its own block.
#    
## Nested `if` statements

A **nested `if` statement** is an `if` statement inside another `if` statement.

The code below illustrates how to create nested `if` statements.

x <- 30

# creating the first if block
if (x > 10) {
  print("x is greater than ten")

  # creating another if block
  if (x > 20) {
    print("and also greater than 20!")

  # closing the second if block
  } else {
    print("but less than 20.")
  }

# closing the first if block
} else {
  print("x is less than 10.")
}

#    
## Explanation
* Line 1: We create an integer variable `x`.
* Line 4: We create the first `if` block and give a condition `(x > 10)`, followed by the statement to be executed in *line 5* if the given condition is `true`.
* Line 8: We create the second `if` block and give a condition `(x > 20)`, followed by the statement to be executed in *line 9* if the provided condition is `true`.
* Line 12: We use the `else` statement/block to close the second `if` block. If the expression in the second `if` block is not `true`, then `R` should execute the statement provided in *line 13*.

* Line 17: We use the `else` statement/block to close the first `if` block. If the expression in the first `if` block is not `true`, then `R` should execute the statement provided in *line 18.*


 

How to create nested if statements in R

Nested if statements in R involve placing one if statement inside another, executing code based on multiple logical expressions.

How to create nested if statements in R

Introduction

Code

The if-else statement

Code

Nested if statements

Explanation

The `if-else` statement

Nested `if` statements