Using if statements

Conditional statements are fundamental in programming, allowing for decision-making based on different conditions. In R, the primary conditional statement is the if statement, which can be used alone or combined with else and else if for more complex logic.

Basic If Statement

The basic if statement checks a condition and executes a block of code if the condition is true.

Syntax:

if (condition) {
  # code to execute if the condition is true
}

Example:

x <- 10

if (x > 5) {
  print("x is greater than 5")
}

If-Else Statement

To execute a block of code when the condition is false, use an else statement.

Syntax:

if (condition) {
  # code to execute if the condition is true
} else {
  # code to execute if the condition is false
}

Example:

x <- 3

if (x > 5) {
  print("x is greater than 5")
} else {
  print("x is not greater than 5")
}

If-Else If-Else Statement

For multiple conditions, use else if to check additional conditions.

Syntax:

if (condition1) {
  # code to execute if condition1 is true
} else if (condition2) {
  # code to execute if condition2 is true
} else {
  # code to execute if none of the conditions are true
}

Example:

x <- 7

if (x > 10) {
  print("x is greater than 10")
} else if (x > 5) {
  print("x is greater than 5 but less than or equal to 10")
} else {
  print("x is 5 or less")
}

Nested If Statements

You can also nest if statements inside one another to check multiple levels of conditions.

Example:

x <- 15
y <- 20

if (x > 10) {
  if (y > 15) {
    print("x is greater than 10 and y is greater than 15")
  } else {
    print("x is greater than 10 but y is not greater than 15")
  }
} else {
  print("x is 10 or less")
}

Vectorized If Statements

When working with vectors, ifelse is a more efficient way to apply conditional logic.

Syntax:

ifelse(test, yes, no)

• test: A logical condition.
• yes: The value to return if the condition is true.
• no: The value to return if the condition is false.

Example:

x <- c(2, 7, 5, 10)

result <- ifelse(x > 5, "Greater than 5", "5 or less")
print(result)

Conclusion

Using if statements in R allows you to execute code based on conditions, making your programs more dynamic and flexible. Whether you’re using a simple if statement, adding else and else if for more complex logic, or applying conditional logic to vectors with ifelse, mastering these constructs is essential for effective programming in R.