Creating Your First R Package

Developing your own R packages is a fundamental skill for statistical analysis and data science. It allows you to organize your code, share your functions with others, and contribute to the R ecosystem. This module will guide you through the essential steps of creating a basic R package.

Why Create an R Package?

Packages are the primary mechanism for extending R's functionality. They offer several key benefits:

Organization: Bundle related functions, datasets, and documentation into a single, manageable unit.
Reproducibility: Ensure your analyses are reproducible by packaging the code and data together.
Sharing: Easily share your tools and insights with colleagues, collaborators, or the wider R community.
Maintainability: Facilitate updates and improvements to your code over time.

Essential Components of an R Package

A basic R package requires a specific directory structure and key metadata files.

At its core, an R package is a directory containing your R code, documentation, and a description file. This structure is standardized to ensure R can find and load your package correctly.

The fundamental structure of an R package includes:

DESCRIPTION file: This is a crucial metadata file that provides essential information about your package, such as its name, version, author, dependencies, and a brief description.
R/ directory: This directory contains your R source code files (e.g., .R files). Each file typically defines one or more functions.
man/ directory: This directory holds the documentation files for your functions, usually in Rd format. These files are used to generate help pages that users can access in R.
NAMESPACE file (optional but recommended): This file controls which functions are exported from your package (made available to users) and which functions are imported from other packages.

Steps to Create a Basic Package

We'll use the

code

devtools

package, a powerful suite of tools for package development, to streamline this process. If you don't have it installed, run

code

install.packages('devtools')

What is the primary R package used for creating and managing R packages?

The devtools package.

Create a New Package Directory: Use the
code
```
create()
```
function from
code
```
devtools
```
to set up the basic package structure.
R
```
library(devtools)
create_package('myRpackage')
```
This will create a new directory named
code
```
myRpackage
```
with the essential subdirectories and a placeholder
code
```
DESCRIPTION
```
file.

Edit the
code
DESCRIPTION
File: Navigate into the
code
```
myRpackage
```
directory. Open the
code
```
DESCRIPTION
```
file in a text editor and fill in the required fields:
- code
```
Package
```
  : The name of your package (e.g.,
  code
```
myRpackage
```
  ).
- code
```
Title
```
  : A concise, descriptive title.
- code
```
Author
```
  : Your name and affiliation.
- code
```
Description
```
  : A more detailed explanation of what your package does.
- code
```
License
```
  : Specify a license (e.g., MIT, GPL-3).
- code
```
Depends
```
  : List any R versions required (e.g.,
  code
```
R (>= 3.5.0)
```
  ).
- code
```
Imports
```
  : List packages your package directly uses (e.g.,
  code
```
dplyr, ggplot2
```
  ).

Add Your R Code: Create an R script (e.g.,
code
```
my_function.R
```
) inside the
code
```
R/
```
directory. Define your functions within this file. For example:
R
```
# R/my_function.R
#' A simple greeting function
#'
#' @param name The name to greet.
#' @return A greeting string.
#' @export
greet <- function(name) {
  paste0('Hello, ', name, '!')
}
```
The comments starting with
code
```
#'
```
are Roxygen2 tags, used for generating documentation.

Generate Documentation: Use Roxygen2 to create the
code
```
.Rd
```
files in the
code
```
man/
```
directory. Run the following command in R from your package's root directory:
R
```
devtools::document()
```
This command reads the Roxygen2 comments and generates the necessary documentation files.

Build and Install Your Package: To test your package, you can build and install it locally:
R
```
devtools::install()
```
After installation, you can load your package and use its functions:
R
```
library(myRpackage)
greet('World')
```

The devtools::document() function is crucial for translating Roxygen2 comments into user-friendly help files.

Key Concepts in Package Development

Component	Purpose	Location
DESCRIPTION	Package metadata (name, author, version, dependencies)	Root directory
R/	R source code files (.R)	Subdirectory
man/	Documentation files (.Rd)	Subdirectory
NAMESPACE	Controls function export/import	Root directory

Next Steps

Once you have a basic package working, you can explore more advanced topics such as adding datasets, creating vignettes (tutorials), handling C/C++/Fortran code, and preparing your package for submission to CRAN.

Learning Resources

R Packages by Hadley Wickham & Jenny Bryan(documentation)

The definitive guide to R package development, covering everything from basics to advanced topics with clear explanations and examples.

Introduction to Package Development with R(documentation)

The official R extension manual, providing in-depth technical details on package structure and development.

Using devtools for Package Development(tutorial)

A practical introduction to the `devtools` package, which simplifies many aspects of R package creation and management.

Roxygen2: Documenting R code(documentation)

Learn how to use Roxygen2 comments to automatically generate documentation for your R functions and packages.

Creating R Packages: A Step-by-Step Guide(blog)

A beginner-friendly tutorial that walks through the process of creating a simple R package from scratch.

Building R Packages for Data Science(video)

A video tutorial demonstrating the practical steps involved in building an R package, focusing on data science applications.

Understanding R Package Structure(documentation)

An overview of the essential tools and directory structures required for developing R packages.

CRAN Policies(documentation)

Essential guidelines and policies for submitting packages to the Comprehensive R Archive Network (CRAN).

R-devel mailing list(documentation)

A forum for discussing R development, including package creation and best practices.

The Art of R Programming - Chapter 12: Packages(blog)

A chapter from a comprehensive R programming book that covers the fundamentals of package development.

Creating a Basic R Package