In R, we will often perform a task based on a condition. For example, if we are analyzing data for the summer, then we will only want to look at data that falls in June, July, and August.

We can perform a task based on a condition using an if statement:

if (TRUE) { print('This message will print!') }

Notice in the example above, we have an if statement. The if statement is composed of:

  • The if keyword followed by a set of parentheses () which is followed by a code block, or block statement, indicated by a set of curly braces {}.
  • Inside the parentheses (), a condition is provided that evaluates to TRUE or FALSE.
  • If the condition evaluates to true, the code inside the curly braces {} runs, or executes.
  • If the condition evaluates to false, the code inside the block won’t execute.

Knowing how to use if statements will help you introduce logic in your data analysis. There is also a way to add an else statement. An else statement must be paired with an if statement, and together they are referred to as an if…else statement.

if (TRUE) { print("Go to sleep!") } else { print("Wake up!") }

In the example above, the else statement:

  • Uses the else keyword following the code block of an if statement.
  • Has a code block that is wrapped by a set of curly braces {}.
  • The code inside the else statement code block will execute when the if statement’s condition evaluates to false. These if…else statements allow us to automate solutions to yes-or-no questions, also known as binary decisions.



Create a conditional statement in notebook.Rmd such that it will change the value of the variable message to 'I execute this when true!' when the condition is TRUE, and the value of message to 'I execute this when false!' when it is FALSE.


Print the value of message after the if…else statement by using print(message).

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