This document provides an introduction to creating an R package. It discusses preliminaries like where R packages come from and where they are stored on a user's computer. The document explains the development workflow for a package, including using devtools to load and test code. It demonstrates creating a basic package using usethis and modifying sample code from an existing package to add a character and test the change. The goal is to get users comfortable with the basic process and differences compared to regular script development in R.

1. Isabella Gollini
Isabella.Gollini@ucd.ie
@IsabellaGollini
R Package Development
Create your Own Package
DataFest Tbilisi
November 2018
https://github.com/forwards/workshops/
https://forwards.github.io

2. Preliminaries

3. The material is mostly drawn from
http://r-pkgs.had.co.nz
https://amzn.com/1491910399

4. The bad news:
It’s going to be
frustrating
http://hyperboleandahalf.blogspot.com/2010/09/four-levels-of-social-entrapment.html
© Allie Brosh

5. This work is licensed under the
Creative Commons Attribution-Noncommercial 3.0
United States License.
To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/3.0/us/
The good news:
Frustration is
typical and
temporary
http://hyperboleandahalf.blogspot.com/2010/06/this-is-why-ill-never-be-adult.html
© Allie Brosh

6. Why make a package?
• You want to test
• You want to generalise
• You want to document
• You want to share

7. Get to know your R
installation

8. R.home()
list.files(R.home())
R.version

9. Where do R packages
come from?

10. CRAN and GitHub,
mostly
install.packages("foo")
library(devtools)
install_github("jane/foo")

11. Where do R packages
live on your computer?

12. R packages live
in a library

13. Get to know your R
library(ies?)

14. .Library
.libPaths() All the libraries
R knows about
The default library

15. .Library == .libPaths()
For many useRs, these are same
Other useRs maintain multiple libraries
E.g., You can put add-on packages in a user-level library:
/Users/isabella/resources/R/library
?

16. Make sure you have recent versions of
these packages
old.packages()
packageVersion()
install.packages("devtools")
install.packages("pkgdown")
install.packages("roxygen2")
install.packages("testthat")
install.packages("tidyverse")
install.packages("usethis")

17. My first package

18. # Create a package on your Desktop:
usethis::create_package("~/Desktop/mypackage")
# Or on RStudio.cloud (create within main project)
usethis::create_package("mypackage")
This will create a new R project and start a new session.
What other files and directories are created?
Your turn

19. What happens we run create_package()?
R/
mypackage.Rproj
DESCRIPTION
create_package("mypackage")
NAMESPACE

20. RStudio helpers: build (& git) menus

21. Package: mypackage
Version: 0.0.0.9000
Title: What the Package Does (One Line, Title Case)
Description: What the package does (one paragraph).
Authors@R: person("First", "Last", ,
"first.last@example.com", c("aut", "cre"))
License: What license it uses
Encoding: UTF-8
LazyData: true
ByteCompile: true
DESCRIPTION

22. Development
workflow

23. How is developing a
package
same / different
from developing a script?

24. How same?
Iterate early and often!
Change it, try it, change it, try it, ad nauseum

25. How different?
Write functions, not “top-level” code.
Dependencies are different,
no library() calls.
Install & Restart (or simulate that),
don’t source().

26. Figure from Hadley Wickham’s book, R packages
http://r-pkgs.had.co.nz
https://github.com/hadley/r-pkgs/blob/master/diagrams/installation.png
You write this … but you use this

27. Figure from Hadley Wickham’s book, R packages
http://r-pkgs.had.co.nz
https://github.com/hadley/r-pkgs/blob/master/diagrams/loading.png
Normal day-to-day usage
Development: Every 2 minutes
How do packages get into memory?
Development: every couple hours or days?
Install and Restart

28. Basic workflow
Modify code
You don’t even needto save your code!
devtools::load_all()
Cmd/Ctrl + Shift +L
Explore in console

29. Your turn
[Uses https://github.com/forwards/mylittlepony]
• Open mylittlepony.Rproj.
• Load all the functions using,
devtools::load_all()then run
rpony(10)
Uhoh! I have forgotten to include Fluttershy in the list
of ponies.
• Add her, reload the code, and verify that your change
worked.

30. This work is licensed under the
Creative Commons Attribution-Noncommercial 3.0
United States License.
To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc/3.0/us/