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R – if-else statement

  • Last Updated : 18 Oct, 2021

The if-statement in Programming Language alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false. Here comes the R else statement. We can use the else statement with the if statement to execute a block of code when the condition is false.

Syntax of if-else statement in R Language: 

if (condition)
{
    // Executes this block if
    // condition is true
} else
{
    // Executes this block if
    // condition is false
}

Working of if-else statement in R Programming

  • Control falls into the if block.
  • The flow jumps to Condition.
  • Condition is tested. 
    • If Condition yields true, goto Step 4.
    • If Condition yields false, goto Step 5.
  • The if-block or the body inside the if is executed.
  • The else block or the body inside the else is executed.
  • Flow exits the if-else block.

Flowchart if-else statement in R: 

R – if-else Statement Example

Example 1: 

R






x <- 5
  
# Check value is less than or greater than 10
if(x > 10)
{
    print(paste(x, "is greater than 10"))
} else
{
    print(paste(x, "is less than 10"))
}

Output: 

[1] "5 is less than 10"

Here in the above code, Firstly, x is initialized to 5, then if-condition is checked(x > 10), and it yields false. Flow enters the else block and prints the statement “5 is less than 10”.

Example 2: 

R




x <- 5
 
# Check if value is equal to 10
if(x == 10)
{
    print(paste(x, "is equal to 10"))
} else
{
    print(paste(x, "is not equal to 10"))
}

Output: 

[1] "5 is not equal to 10" 

Nested if-else statement in R

The if-else statements can be nested together to form a group of statements and evaluate expressions based on the conditions one by one, beginning from the outer condition to the inner one by one respectively. An if-else statement within another if-else statement better justifies the definition.

Syntax:

if(condition1){
# execute only if condition 1 satisfies
if(condition 2){ 
# execute if both condition 1 and 2 satisfy
}
}else{
}

Example:

R




# creating values
var1 <- 6
var2 <- 5
var3 <- -4
 
# checking if-else if ladder
if(var1 > 10 || var2 < 5){
print("condition1")
}else{
if(var1 <4 ){
    print("condition2")
}else{
    if(var2>10){
    print("condition3")
    }
    else{
    print("condition4")
    }
}
}

Output:

[1] "condition4"



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