Write a Function in R with Me

While working with data in R, sometimes I need to create my functions to speed up the calculations. I know, that at the beginning, writing your functions may seem difficult. Therefore here is step by step guide how to do it.

In this post, we will go step by from the structure of the R functions, arguments, testing the function, and finally using it with data.

After that, I hope you have some sense of understanding and could write your formulas. Let’s dive in!

Step 1: Structure of a Function in R

The structure of the R function looks like this:

my_function <- function(arg1, arg2, ...) {
  # body of the function
  # computations and operations
  return(result)
}

where arg1, arg2, and so on are arguments, e.g., .

Then we open a { and write formulas, what our function does.

In return(result), we specify an object that will be the output of this function. It could be a single number, array, or data frame.

Step 2: Define Your Function Name and Arguments

Let's create a simple function to calculate the sum of squares of two numbers.

sum_of_squares <- function(x, y) {
  result <- x^2 + y^2
  return(result)
}

x, y are arguments, the name of the function is sum_of_squares, and the output is the result.

Step 3: Test the Function

To check if our function works all right, just check if it works manually on a couple of different values.

This function is simple. However, testing more complicated functions may last a little bit longer. Then finding and repairing its formulas may last longer too.

# Test 1
sum_of_squares(3, 4)
# Expected Output: 25

# Test 2
sum_of_squares(-2, 5)
# Expected Output: 29

Step 4: Include Error Handling

To make your function more robust, include error checks for invalid inputs.

In our case, we want x, and y to be numeric type.

sum_of_squares <- function(x, y) {
  if (!is.numeric(x) || !is.numeric(y)) {
    stop("Both x and y must be numeric values.")
  }
  result <- x^2 + y^2
  return(result)
}

When testing with a non-numeric argument, the function’s output should say that both x and y must be numeric values.

Conclusion

Writing a function in R might be a challenge at first glance. However, when you break the process of creating the function into steps, it becomes easier to understand.

In this post, we wrote a simple function together with error-handling capabilities. Feel free to experiment with these formulas and create different versions of this function or a completely new one.

Good luck!