R If Else Conditions

In R programming, conditional statements allow a program to make decisions and execute different actions based on certain conditions. The if-else construct is a key conditional statement used to control the flow of code. Using these statements, you can handle different situations dynamically.

• if Statement: Executes a block of code only when the condition is TRUE.
• else Statement: Executes a block of code when the if condition is FALSE.

Syntax

if (condition) {

# code to execute if condition is TRUE

} else {

# code to execute if condition is FALSE

}

How if-else Statements Work in R

if-else statements control the flow of a program by executing different code blocks based on a condition.

• Start of Control: Program execution reaches the if statement.
• Condition Evaluation: The logical condition inside if is tested.
• If TRUE: The code inside the if block is executed.
• If FALSE: The code inside the else block is executed (if present).
• Flow Exit: After executing the respective block, the program continues with the next statements outside the if-else.

Example 1: Basic if-else

Here we implement a basic if-else statement in R to check whether a number is greater than or less than 10.

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 x is initialized to 5, the condition x > 10 is false, so the program executes the else block and prints: "5 is less than 10."

Example 2: Checking Equality

Here we use an if-else statement in R to check whether a number is equal to 10 or not.

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"

Here x is 5, the condition x == 10 is false, so the else block runs and prints: "5 is not equal to 10."

Nested if-else Statements in R

The if-else statements in R can be nested to form a group of statements that evaluate conditions one by one, starting from the outer condition to the inner ones. An if-else statement placed within another if-else statement in R is called a nested statement.

• Nested if-else statements allow sequential evaluation of multiple conditions.
• Execution stops at the first TRUE condition in the hierarchy.

Syntax

if(condition1) {

# execute if condition1 is TRUE

if(condition2) {

# execute if both condition1 and condition2 are TRUE

}

} else {

# execute if condition1 is FALSE

}

Example 1: Nested if-else

Here nested if-else in R evaluates multiple conditions to find the range of x

x <- 15
if (x < 10) {
  print("x is less than 10")
} else {

  if (x < 20) {
    print("x is between 10 and 20")
  } else {
    print("x is greater than or equal to 20")
  }
}

Output:

[1] "x is between 10 and 20"

• Outer if checks x < 10, which is FALSE.
• Flow enters the else block and evaluates the nested if (x < 20), which is TRUE.
• The program prints "x is between 10 and 20".

Example 2: Nested if-else for Eligibility

In this R code we uses nested if-else statements to assess whether a student qualifies for a scholarship based on grades and income

grades <- 85
income <- 25000

if (grades >= 80) {
  if (income <= 30000) {
    print("Congratulations, you are eligible for a scholarship!")
  } else {
    print("Sorry, your income is too high to qualify for a scholarship.")
  }
} else {
  print("Sorry, your grades are too low to qualify for a scholarship.")
}

Output:

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

• Define grades and income to represent a student’s scores and financial status.
• Use a nested if-else to check scholarship eligibility based on grades and income.
• Outer if checks if grades ≥ 80; inner if checks if income ≤ 30,000.

Conditions and If Statements

Here we will show the use of logical conditions in if statements. Adjust the values and conditions as needed for our specific requirements.