# Functions

This section takes an estimated 45 minutes to complete.

Functions play a critical role in any R program and you tend to write a lot of them while programming. This section focuses on functions in R.

## Functions in R

To start, watch the following videos outlining the concept of functions in R:

## R exercises

Create a function which will take the height and weight values and calculate body mass index.

Write an R function that will generate a Fibonacci sequence of desired size.

Write an R function which will perform transcription of dna letters into RNA.

Write a function is.even(n) in R that returns TRUE when n is even and FALSE otherwise. Then, using is.even(n), write a function evens.in(v) that returns a vector composed of the even integers in a vector v of integers.

Create a function that given a vector and an integer will return how many times the integer appears inside the vector.

Create a function that given an integer will calculate how many divisors it has (other than 1 and itself). Make the divisors appear by screen.

## swirl Exercises

Complete **swirl Lesson 9: Functions**, to solidify what you just learned, and return here afterward.

## Congratulations!

If you made it here, then congratulations! You have successfully completed this section. Move to the next portion of the guide with the arrow buttons below.

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