Your first R package

Makes your code:

• Easier to manage

• Easier to reuse

• Easier to share

1. What is an R package?

2. Your first R package

3. Developing R packages using RStudio

"Packages are the fundamental units of reproducible R code." (Hadley Wickham)

"R packages are the best way to distribute R code and documentation…" (Karl Broman)

Functions are an even more 'fundamental unit' than packages

The simplest way to 'package up' some R code

Define a function:

# Calculate the square of x.
square <- function(x)
    x^2

Use the function:

square(1:3)

## [1] 1 4 9

…a standard way to 'package up' R functions together

R code ➔ functions ➔ packages

1. Place function definitions in a file called functions.R

2. Load this in other scripts using source("functions.R")

In functions.R:

# Calculate the square of x.
square <- function(x)
    x^2

In your R session:

source("functions.R")
square(1:3)

## [1] 1 4 9

In functions.R:

# Resample values from a given vector.
resample <- function(x, ...)
    x[sample.int(length(x), ...)]

In your R session:

source("functions.R")
resample(letters[1:10])

##  [1] "c" "h" "d" "a" "i" "e" "g" "j" "f" "b"

In your R session:

source("functions.R")
square(1:3)

## [1] 1 4 9

resample(letters[1:10])

##  [1] "d" "i" "c" "e" "f" "g" "h" "a" "j" "b"

Create folder structure

mypackage/
└── R/

Move functions.R into the R subfolder

mypackage/
└── R/
    └── functions.R

Create the DESCRIPTION and NAMESPACE files

mypackage/
├── R/
│   └── functions.R
├── DESCRIPTION
└── NAMESPACE

Note: RStudio will automatically create these files

Your DESCRIPTION file should look similar to:

Package: mypackage
Title: This is my first R package
Description: This package was created as a way to learn how to write
    R packages.
Authors@R: person("Damjan", "Vukcevic", email = "damjan@vukcevic.net",
                  role = c("aut", "cre"))
Version: 0.1
Depends: R (>= 3.3.1)
License: GPL-3
LazyData: true

Your NAMESPACE file should look like:

# Export all names
exportPattern("^[[:alpha:]]+")

Now, let's do all of this in RStudio…

1. File > New Project… > New Directory > R Package > (dialog box) > Create Project

   

2. Edit the DESCRIPTION file

3. Edit your code

1. Edit your code
2. Build > Build and Reload
   (Ctrl/Cmd + Shift + B)
3. Try running your functions in the Console
4. Repeat until happy

Simply use library(mypackage) instead of source("functions.R")

For example:

library(mypackage)
square(1:3)

## [1] 1 4 9

resample(letters[1:10])

##  [1] "f" "b" "a" "c" "e" "g" "i" "h" "d" "j"

You can split up your code into any number of .R files

mypackage/
├── R/
│   ├── resample.R
│   └── square.R
├── DESCRIPTION
└── NAMESPACE

All .R files within the R subfolder will automatically be included in your package

(More convenient than if source()-ing)

• Easier to reuse
• Easier to share
• Easier to maintain as complexity increases
• Cleaner project code

And also (not covered today):

• Better documentation
• Easier automated testing
• Dependency and namespace management

Slides for this talk

https://dvukcevic.github.io/rpkgs-talk-resbaz2018/

More advanced guide for writing R packages

https://dvukcevic.github.io/rpkgs-talk/

Contact me

Web - http://damjan.vukcevic.net/

Email - damjan@vukcevic.net

Twitter - @VukcevicD

Challenge 1

Write an R package called challenge1 that contains the functions square() and cube() which respectively square or cube an input number.

Challenge 2

Write an R package called challenge2 that contains the functions fullname() and sentence() that behave as follows:

• fullname() combines two input strings into a single string, for example:
  fullname("Damjan", "Vukcevic") should return "Damjan Vukcevic".

• sentence() takes two input strings and returns a sentence, in this form:
  sentence("Damjan", "Vukcevic") should return "The name Damjan Vukcevic contains 14 characters".

Hint: use paste() and nchar()