R If Else Conditions

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 Programming 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) {
  # code to be executed if condition is TRUE
} else {
  # code to be executed if condition is FALSE
}

if-else statement in R

Working of if-else statements in R Programming

• Control falls into the if block.
• The flow jumps to Condition.
• Condition is tested. 
  • If the Condition yields true, goto Step 4.
  • If the 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

R if-else Statement Example

Example

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 the 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

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 in R 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 in R 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

# define a variable
x <- 15

# check the value of x using nested if-else statements
if (x < 10) {
  # if x is less than 10
  print("x is less than 10")
} else {
  # if x is greater than or equal to 10
  if (x < 20) {
    # if x is less than 20
    print("x is between 10 and 20")
  } else {
    # if x is greater than or equal to 20
    print("x is greater than or equal to 20")
  }
}

Output

[1] "x is between 10 and 20"

• In this example, we first define a variable x with the value of 15.
• Then we use a nested if-else statement to check the value of x. 
• The outer if-else statement checks if x is less than 10. If it is, we print the message “x is less than 10”. If x is not less than 10, we move on to the nested if-else statement inside the else block. 
• This nested if-else statement checks if x is less than 20. If it is, we print the message “x is between 10 and 20”. If x is not less than 20, we print the message “x is greater than or equal to 20”. Since x is 15, the code will print “x is between 10 and 20”.

Example

R

# define variables for grades and income
grades <- 85
income <- 25000

# check eligibility for scholarship using nested if-else statements
if (grades >= 80) {
  # if grades are 80 or above
  if (income <= 30000) {
    # if income is 30,000 or less
    print("Congratulations, you are eligible for a scholarship!")
  } else {
    # if income is more than 30,000
    print("Sorry, your income is too high to qualify for a scholarship.")
  }
} else {
  # if grades are below 80
  print("Sorry, your grades are too low to qualify for a scholarship.")
}

Output

[1] "Congratulations, you are eligible for a scholarship!"

• In this example, we first define two variables, grades and income, to represent a student’s grades and income, respectively. 
• Then we use a nested if-else statement to check if the student is eligible for a scholarship. 
• The outer if-else statement checks if the student’s grades are 80 or above. If they are, we move on to the nested if-else statement inside the if block. This nested if-else statement checks if the student’s income is 30,000 or less.
•  If it is, we print the message “Congratulations, you are eligible for a scholarship!” If the student’s income is more than 30,000, we print the message “Sorry, your income is too high to qualify for a scholarship.” If the student’s grades are below 80, we print the message “Sorry, your grades are too low to qualify for a scholarship.”
•  This nested if-else statement can be expanded upon to include additional conditions, such as residency or enrollment status, to determine scholarship eligibility.