How to Use If Else in R: Simple Guide with Examples

In R, use if to run code when a condition is true, and else to run code when it is false. The syntax is if (condition) { code } else { code }. This helps your program make decisions based on conditions.

Syntax

The if else statement in R lets you choose between two actions based on a condition.

• if (condition): Checks if the condition is true.
• { code }: Runs this code if the condition is true.
• else: Runs this code if the condition is false.

r

if (condition) {
  # code to run if condition is TRUE
} else {
  # code to run if condition is FALSE
}

Example

This example checks if a number is positive or not and prints a message accordingly.

r

number <- 5
if (number > 0) {
  print("The number is positive")
} else {
  print("The number is zero or negative")
}

Output

[1] "The number is positive"

Common Pitfalls

Common mistakes include missing curly braces or using else without an if. Also, placing else on a new line without the previous block ending properly can cause errors.

Always put else right after the closing brace of if block.

r

## Wrong way (causes error):
number <- -3
if (number > 0) 
  print("Positive")
else
  print("Not positive")

## Right way:
if (number > 0) {
  print("Positive")
} else {
  print("Not positive")
}

Output

[1] "Not positive"

Quick Reference

Use if to check a condition and run code if true. Use else to run code if false. Always use curly braces { } to group code blocks.

Keyword	Purpose	Example
if	Runs code if condition is TRUE	if (x > 0) { print("Positive") }
else	Runs code if condition is FALSE	else { print("Not positive") }

Key Takeaways

Use if else in R to run different code based on conditions.

Always put else immediately after the if block's closing brace.

Use curly braces { } to group code inside if and else.

Conditions inside if must be logical expressions returning TRUE or FALSE.

Indent your code inside if else blocks for better readability.