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<!DOCTYPE html>
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<title>Introduction to R Functions</title>
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# Introduction to R Functions
## R Ladies Chicago and R Ladies East Lansing
### Stephanie Kirmer <br> <a href="http://github.com/skirmer"><svg viewBox="0 0 496 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M165.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6zm-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3zm44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z"></path></svg> skirmer</a><br> <a href="http://twitter.com/data_stephanie"> <svg viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M459.37 151.716c.325 4.548.325 9.097.325 13.645 0 138.72-105.583 298.558-298.558 298.558-59.452 0-114.68-17.219-161.137-47.106 8.447.974 16.568 1.299 25.34 1.299 49.055 0 94.213-16.568 130.274-44.832-46.132-.975-84.792-31.188-98.112-72.772 6.498.974 12.995 1.624 19.818 1.624 9.421 0 18.843-1.3 27.614-3.573-48.081-9.747-84.143-51.98-84.143-102.985v-1.299c13.969 7.797 30.214 12.67 47.431 13.319-28.264-18.843-46.781-51.005-46.781-87.391 0-19.492 5.197-37.36 14.294-52.954 51.655 63.675 129.3 105.258 216.365 109.807-1.624-7.797-2.599-15.918-2.599-24.04 0-57.828 46.782-104.934 104.934-104.934 30.213 0 57.502 12.67 76.67 33.137 23.715-4.548 46.456-13.32 66.599-25.34-7.798 24.366-24.366 44.833-46.132 57.827 21.117-2.273 41.584-8.122 60.426-16.243-14.292 20.791-32.161 39.308-52.628 54.253z"></path></svg> <span class="citation">@data_stephanie</span></a><br> <a href="http://www.stephaniekirmer.com"> <svg viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M326.612 185.391c59.747 59.809 58.927 155.698.36 214.59-.11.12-.24.25-.36.37l-67.2 67.2c-59.27 59.27-155.699 59.262-214.96 0-59.27-59.26-59.27-155.7 0-214.96l37.106-37.106c9.84-9.84 26.786-3.3 27.294 10.606.648 17.722 3.826 35.527 9.69 52.721 1.986 5.822.567 12.262-3.783 16.612l-13.087 13.087c-28.026 28.026-28.905 73.66-1.155 101.96 28.024 28.579 74.086 28.749 102.325.51l67.2-67.19c28.191-28.191 28.073-73.757 0-101.83-3.701-3.694-7.429-6.564-10.341-8.569a16.037 16.037 0 0 1-6.947-12.606c-.396-10.567 3.348-21.456 11.698-29.806l21.054-21.055c5.521-5.521 14.182-6.199 20.584-1.731a152.482 152.482 0 0 1 20.522 17.197zM467.547 44.449c-59.261-59.262-155.69-59.27-214.96 0l-67.2 67.2c-.12.12-.25.25-.36.37-58.566 58.892-59.387 154.781.36 214.59a152.454 152.454 0 0 0 20.521 17.196c6.402 4.468 15.064 3.789 20.584-1.731l21.054-21.055c8.35-8.35 12.094-19.239 11.698-29.806a16.037 16.037 0 0 0-6.947-12.606c-2.912-2.005-6.64-4.875-10.341-8.569-28.073-28.073-28.191-73.639 0-101.83l67.2-67.19c28.239-28.239 74.3-28.069 102.325.51 27.75 28.3 26.872 73.934-1.155 101.96l-13.087 13.087c-4.35 4.35-5.769 10.79-3.783 16.612 5.864 17.194 9.042 34.999 9.69 52.721.509 13.906 17.454 20.446 27.294 10.606l37.106-37.106c59.271-59.259 59.271-155.699.001-214.959z"></path></svg> stephaniekirmer.com</a>
### February 26, 2021
---
layout: true
.footer[<a href="https://github.com/skirmer/functions_r"><svg viewBox="0 0 496 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M165.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6zm-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3zm44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z"></path></svg> github.com/skirmer/functions_r </a> | <a href="http://twitter.com/data_stephanie"><svg viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M459.37 151.716c.325 4.548.325 9.097.325 13.645 0 138.72-105.583 298.558-298.558 298.558-59.452 0-114.68-17.219-161.137-47.106 8.447.974 16.568 1.299 25.34 1.299 49.055 0 94.213-16.568 130.274-44.832-46.132-.975-84.792-31.188-98.112-72.772 6.498.974 12.995 1.624 19.818 1.624 9.421 0 18.843-1.3 27.614-3.573-48.081-9.747-84.143-51.98-84.143-102.985v-1.299c13.969 7.797 30.214 12.67 47.431 13.319-28.264-18.843-46.781-51.005-46.781-87.391 0-19.492 5.197-37.36 14.294-52.954 51.655 63.675 129.3 105.258 216.365 109.807-1.624-7.797-2.599-15.918-2.599-24.04 0-57.828 46.782-104.934 104.934-104.934 30.213 0 57.502 12.67 76.67 33.137 23.715-4.548 46.456-13.32 66.599-25.34-7.798 24.366-24.366 44.833-46.132 57.827 21.117-2.273 41.584-8.122 60.426-16.243-14.292 20.791-32.161 39.308-52.628 54.253z"></path></svg> @data_stephanie</a>]
---
# Overview
- Lecture alternating with breakouts for hands-on examples
--
- Repo: https://github.com/skirmer/functions_r
--
- Support Team for questions/leading breakouts
--
<img src="https://media.giphy.com/media/l46Cbqvg6gxGvh2PS/giphy.gif" style="width: 50%" />
???
Introductions for support team
---
## Breakout Sections
- Work through examples in small groups
- 5-ish minute chunks
- Choose either Beginner or Advanced group
- Beginners will read provided function, and gradually edit it
- Advanced will write your own function, and fully develop it
<img src="https://media.giphy.com/media/3jN3GziOKUEmI/giphy.gif" style="width: 30%" />
???
If you have your own code, or some idea for a function, you can work with Advanced group to develop it into a full function
If you don't have your own code or don't want to write it all yourself, work with Beginner
You can change groups later!
---
# What is a Function Anyway?
???
You have one thing, and you want to have another thing, so the function is your path to get there.
---
# Why Functions?
- Avoid repetition
- Share code with others
- Eventually build packages
<img src="https://media.giphy.com/media/20BoPFWiCG3K9GYABQ/giphy.gif" style="width: 40%" />
???
Those operations you want to run in order to get from what you have to what you need are useful to others!
This framework is common to many programming languages
---
# Basic Structure
```r
myFunction <- function(){
...
return()
}
myFunction()
```
???
This shell is what lets R know that you intend to create a function.
Now we need to add in the contents.
---
# Basic Structure
```r
myFunction <- function(ARGUMENTS){
* ...
return(OUTPUT)
}
myFunction(ARGUMENTS)
```
---
# Basic Structure
```r
myFunction <- function(a, b){
* c <- a*b
return(c)
}
myFunction(a = 2,b = 4)
```
---
class: inverse
# Practice Break 1
Open possible_dog_part1.R and follow the instructions.
- Beginner: Read the sample function, and interpret what it does.
- Discuss the structure. Think about what might make it better or easier to use.
- Advanced: Take a bit of your own code and place it in a function structure. Change function name to something appropriate.
<div class="countdown" id="timer_60391713" style="bottom:0;left:0;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
# Types
- Logical or Boolean (TRUE, FALSE, 0, 1)
- Integer (Numeric) (3, 7, 108)
- Double or Float (Numeric) (1.6645, 3.14159, 987.99)
- Character or String ("Hello", "a")
- Closure (function) (`sum()`)
More info in help: `?type` or `?mode`
Plus: list, complex, special, etc
<img src="https://media.giphy.com/media/ouE6OPO1MADM4/giphy.gif" style="width: 40%" />
???
Before we deep dive into these pieces, we have to make sure we understand types just a little.
While we aren't going to go deep in today, your arguments can be things like lists and dataframes as well as single items - you can get creative!
---
# Arguments, or What Goes In
- Order and naming are important
- Defaults can be set, not required
```r
*myFunction <- function(a=1, b=1){
...
myFunction(a = 2,b = 4)
```
<img src="https://media.giphy.com/media/XhAQgt6ytc6E8/giphy.gif" style="width: 40%" />
???
You can set default values for the arguments as shown
Your arguments need to observe a specific type usually (best practices)
---
class: inverse
# Practice Break 2
Open possible_dog_part2.R and follow the instructions.
- Beginner: Identify the changes in the example function. Try running it, and change the arguments.
- Discuss what change you made and what the effects were. What type/s can the function accept? What happens if you pass something else?
- Advanced: Add an argument to your function, and make it change the output.
<div class="countdown" id="timer_60391523" style="bottom:0;left:0;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
???
If you weren't comfortable or were not challenged in the group you picked last time, you can switch!
---
# Returns, or What Comes Out
- Object (single) that you'll be able to use elsewhere
- May be any of the types we previously discussed
- Not required! Functions can do things besides return
```r
myFunction <- function(a, b){
...
* return(c)
}
```
<img src="https://media.giphy.com/media/ZaoNH308FHz7a/giphy.gif" style="width: 40%" />
???
Key - make sure the user of this function gets something they are reasonably expecting
A function could change the state of an existing object without using a return (global env, will discuss)
Single object return only in R
---
class: inverse
# Practice Break 3
Open possible_dog_part3.R and follow the instructions.
- Beginner: Identify the changes in the example function. What is it returning?
- Try changing the return, see what it does.
- Advanced: Add a two-element return to your function. Remember that R does not allow multi-argument returns.
<div class="countdown" id="timer_6039167f" style="bottom:0;left:0;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
# Guardrails: Documentation
- Explain what the arguments and returns are
- Demonstrate how the function is meant to be used
- May include `@description` or other additional items
```r
#' Explain what my function does
#'
#' @param a Type. Description of what it represents.
#' @param b Type. Description of what it represents.
#'
#' @return Type. Description of what it represents.
#'
#' @examples
#' \dontrun{myFunction(a = 5, b = 3)}
```
<img src="https://media.giphy.com/media/lkdpUMrVSG9D9xiFt0/giphy.gif" style="width: 25%" />
???
Be clear, but not too wordy
Tell the user what they need to know in order to use the function and understand
---
class: inverse
# Practice Break 4
Open possible_dog_part4.R and follow the instructions.
- Beginner: Fill in the blanks in the provided function documentation.
- Advanced: Add documentation for your function, including arguments and returns.
<div class="countdown" id="timer_6039150f" style="bottom:0;left:0;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
# Guardrails: Type Check
- Setting an informative error helps the user
- Checks can look at be more than just type
```r
myFunction <- function(a, b){
* if(!is.double(a)) stop("a must be a number")
c <- a*b
return(c)
}
myFunction(a = 2,b = 4)
#myFunction(a = TRUE, b = 4)
```
<img src="https://media.giphy.com/media/zCpYQh5YVhdI1rVYpE/giphy.gif" style="width: 25%" />
???
User might be future you!
---
class: inverse
# Practice Break 5
Open possible_dog_part5.R and follow the instructions.
- Beginner: Examine the type check included in the function. Pass arguments to the function that will violate it.
- Is the error informative?
- Advanced: Add a type check to your function's arguments. Make sure the error message is clear.
<div class="countdown" id="timer_6039167e" style="bottom:0;left:0;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
# Guardrails: Tests
- Vital for making packages later
- Helps you ensure that changes have not broken expected behavior
```r
library(testthat)
myFunction <- function(a, b){
if(!is.numeric(a)) stop("a must be a number")
c <- a*b
return(c)
}
```
```r
test_that("Function returns correct value",
{
* product = myFunction(a = 2,b = 4)
* expect_equal(product, 8)
})
```
???
If the return is not in line with expectations, you can easily find out.
---
# Guardrails: Tests
```r
library(testthat)
test_that("Function returns expected error",
{
* expect_error(myFunction(a = TRUE, b = 4))
})
```
<img src="https://media.giphy.com/media/LycfkVG4L6x0Y/giphy.gif" style="width: 50%" />
???
Tests can check that it fails or errors when it's supposed to as well!
---
class: inverse
# Practice Break 6
Open possible_dog_part6.R and follow the instructions.
- Beginner: Fill in the argument value that will make the test pass, or change the test.
- Discuss whether it is more sensible to change the argument or the test.
- Advanced: Write a test for your function.
- Do you want to test for expected error or for expected return?
<div class="countdown" id="timer_603914b6" style="bottom:0;left:0;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">05</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
# Environments
The function knows what exists inside itself, and what exists in the "global" environment.
Outside the function only knows what exists in the "global".
Here, a, b, and c do not exist in the world outside our function.
```r
print(environment())
print(objects())
myFunction <- function(a, b){
* c <- a*b
print(environment())
print(objects())
return(c)
}
myFunction(a = 2,b = 4)
```
---
# Global Environment
- No a, b, or c
```r
print(environment())
```
```
## <environment: R_GlobalEnv>
```
```r
print(objects())
```
```
## [1] "myFunction"
```
---
# Function Environment
- Here they are!
```r
myFunction <- function(a, b){
* c <- a*b
print(environment())
print(objects())
return(c)
}
myFunction(a = 2,b = 4)
```
```
## <environment: 0x7fdf422a7448>
## [1] "a" "b" "c"
```
```
## [1] 8
```
---
# Mixing Environments
```r
myFunction <- function(a, b){
* d <<- a*b
print(environment())
print(objects())
return(d)
}
myFunction(a = 2,b = 4)
```
```
## <environment: 0x7fdf424b5780>
## [1] "a" "b"
```
```
## [1] 8
```
```r
print(environment())
```
```
## <environment: R_GlobalEnv>
```
```r
print(objects())
```
```
## [1] "d" "myFunction"
```
???
Watch out how you use the double arrow!
---
# Exploring a Function
- Just omit the parentheses
```r
dplyr::top_n
```
```
## function (x, n, wt)
## {
## lifecycle::signal_superseded("1.0.0", "top_n()", "slice_max()")
## wt <- enquo(wt)
## if (quo_is_missing(wt)) {
## vars <- tbl_vars(x)
## wt_name <- vars[length(vars)]
## inform(glue("Selecting by ", wt_name))
## wt <- sym(wt_name)
## }
## filter(x, top_n_rank({
## {
## n
## }
## }, !!wt))
## }
## <bytecode: 0x7fdf3082af28>
## <environment: namespace:dplyr>
```
---
# Combining Functions
- A function can be an argument to another function
- This way you can chain together elements powerfully
- Helps readability to use functions!
```r
a <- sum(1, 5, 3)
b <- max(a, 4)
b
```
```
## [1] 9
```
```r
c <- max(sum(1, 5, 3), 4)
c
```
```
## [1] 9
```
---
# Conclusion
- Functions are a way of packaging small sections of code to reuse later
- Functions accept input and return output, and contain code
- Documentation and internal tests make functions more useful and easier to work with
<img src="https://media.giphy.com/media/f7rDDvcOV9n8I/giphy.gif" style="width: 50%" />
<svg viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M326.612 185.391c59.747 59.809 58.927 155.698.36 214.59-.11.12-.24.25-.36.37l-67.2 67.2c-59.27 59.27-155.699 59.262-214.96 0-59.27-59.26-59.27-155.7 0-214.96l37.106-37.106c9.84-9.84 26.786-3.3 27.294 10.606.648 17.722 3.826 35.527 9.69 52.721 1.986 5.822.567 12.262-3.783 16.612l-13.087 13.087c-28.026 28.026-28.905 73.66-1.155 101.96 28.024 28.579 74.086 28.749 102.325.51l67.2-67.19c28.191-28.191 28.073-73.757 0-101.83-3.701-3.694-7.429-6.564-10.341-8.569a16.037 16.037 0 0 1-6.947-12.606c-.396-10.567 3.348-21.456 11.698-29.806l21.054-21.055c5.521-5.521 14.182-6.199 20.584-1.731a152.482 152.482 0 0 1 20.522 17.197zM467.547 44.449c-59.261-59.262-155.69-59.27-214.96 0l-67.2 67.2c-.12.12-.25.25-.36.37-58.566 58.892-59.387 154.781.36 214.59a152.454 152.454 0 0 0 20.521 17.196c6.402 4.468 15.064 3.789 20.584-1.731l21.054-21.055c8.35-8.35 12.094-19.239 11.698-29.806a16.037 16.037 0 0 0-6.947-12.606c-2.912-2.005-6.64-4.875-10.341-8.569-28.073-28.073-28.191-73.639 0-101.83l67.2-67.19c28.239-28.239 74.3-28.069 102.325.51 27.75 28.3 26.872 73.934-1.155 101.96l-13.087 13.087c-4.35 4.35-5.769 10.79-3.783 16.612 5.864 17.194 9.042 34.999 9.69 52.721.509 13.906 17.454 20.446 27.294 10.606l37.106-37.106c59.271-59.259 59.271-155.699.001-214.959z"></path></svg> [www.stephaniekirmer.com](http://www.stephaniekirmer.com) | <svg viewBox="0 0 512 512" xmlns="http://www.w3.org/2000/svg" style="height:1em;fill:currentColor;position:relative;display:inline-block;top:.1em;"> [ comment ] <path d="M459.37 151.716c.325 4.548.325 9.097.325 13.645 0 138.72-105.583 298.558-298.558 298.558-59.452 0-114.68-17.219-161.137-47.106 8.447.974 16.568 1.299 25.34 1.299 49.055 0 94.213-16.568 130.274-44.832-46.132-.975-84.792-31.188-98.112-72.772 6.498.974 12.995 1.624 19.818 1.624 9.421 0 18.843-1.3 27.614-3.573-48.081-9.747-84.143-51.98-84.143-102.985v-1.299c13.969 7.797 30.214 12.67 47.431 13.319-28.264-18.843-46.781-51.005-46.781-87.391 0-19.492 5.197-37.36 14.294-52.954 51.655 63.675 129.3 105.258 216.365 109.807-1.624-7.797-2.599-15.918-2.599-24.04 0-57.828 46.782-104.934 104.934-104.934 30.213 0 57.502 12.67 76.67 33.137 23.715-4.548 46.456-13.32 66.599-25.34-7.798 24.366-24.366 44.833-46.132 57.827 21.117-2.273 41.584-8.122 60.426-16.243-14.292 20.791-32.161 39.308-52.628 54.253z"></path></svg> @[data_stephanie](http://www.twitter.com/data_stephanie)
---
# Further Reading
* http://adv-r.had.co.nz/Functions.html
* https://r4ds.had.co.nz/functions.html
* https://nicercode.github.io/guides/functions/
* https://cran.r-project.org/doc/manuals/r-release/R-intro.html#Writing-your-own-functions
* https://r-pkgs.org/man.html
</textarea>
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