General Rules

Let’s pull everything from this tutorial together into a short, reusable reference.

General Rules for Calling Functions

  1. A function call always follows the pattern function_name(arguments).
  2. Every opening parenthesis needs a matching closing parenthesis.
  3. Function names (and argument names) are case-sensitive: mean() and Mean() are not the same thing.
  4. Arguments are separated by commas.
  5. You can name arguments (round(x = 3.14159, digits = 2)) or rely on their order (round(3.14159, 2)), but if you skip a name, the order matters.
  6. Text values must be wrapped in quotes ("like this"); object names and numbers are not.

Putting It All Together

Practice

Using what you’ve learned across this tutorial, write a single R expression that:

  1. Creates a vector of the numbers 4, 8, 15, 16, 23, and 42, called nums.
  2. Calculates the mean of nums, rounded to 1 decimal place.

You’ll need three functions here: one to build the vector, one to average it, and one to round the result. You’ve used all three earlier in this tutorial.

nums <- c(4, 8, 15, 16, 23, 42)
round(mean(nums), 1)
[1] 18

Notice that this solution nests one function call inside another: mean(nums) is calculated first, and its result is immediately passed as the input to round(). You’ll see this pattern constantly once you get comfortable with it.

Ready to Continue?

You’re ready to move on to Add-On Packages if you can:

  • Explain, in plain language, what a function is and why we use them.
  • Recognize a function call in a line of R code.
  • Call a function with one or more arguments.
  • Identify at least one common mistake that causes a function call to fail, and explain why.

If any of these still feel shaky, revisit the relevant page above, or try the Knowledge Quiz to pinpoint exactly where to focus.

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