Understanding Devtools in R: Customizing Package Installation with devtools::install_github

The devtools package is an essential tool for any serious R user. It provides a set of functions to make development and deployment of packages easier, including the ability to install packages from GitHub repositories. In this post, we’ll delve into how devtools::install_github works and explore ways to customize its behavior when installing packages.

Introduction to devtools

Before we dive into the specifics of install_github, let’s take a brief look at what devtools is all about. The devtools package provides a set of tools to make package development easier, including:

• install_github(): Installs packages from GitHub repositories.
• make_pakage(): Creates new packages based on existing ones.
• test_package(): Runs unit tests for packages.

These functions are essential for any R developer who wants to build and deploy their own packages or contribute to open-source projects.

The install_github() Function

The install_github() function is used to install packages from GitHub repositories. Here’s a basic example:

# Install the 'rstudio/rsconnect' package using devtools::install_github()
devtools::install_github('rstudio/rsconnect')

When you run this command, R will automatically download the package and its dependencies from the specified GitHub repository.

The lib Argument in install.packages()

As you mentioned in your question, install.packages() does have a lib argument that allows you to specify where the package should be installed. Here’s an example:

# Install the 'rsconnect' package with the specified library location
install.packages("rsconnect", lib = "U:/Documents/R/R-3.6.2")

However, when using devtools::install_github(), there is no explicit lib argument.

How Does devtools::install_github() Determine Package Location?

When you use devtools::install_github(), R looks for the specified GitHub repository in a few places to determine where to install the package. Here’s what happens:

1. GitHub Repository URL: The first part of the GitHub repository URL is used as the base directory for installation. For example, if you’re installing from https://github.com/rstudio/rsconnect, R will look for a directory called rstudio at that location.
2. GitHub Repository Contents: If the specified repository doesn’t exist or isn’t accessible, R looks for a file called PKG-INF/Makefile within the repository’s contents. This file contains metadata about the package, including its installation location.
3. Default Installation Location: By default, devtools::install_github() installs packages in the .R/checkinst/ directory of your working directory.

Conclusion

Unfortunately, there isn’t a straightforward way to control where packages are installed when using devtools::install_github(). However, you can use other tools and techniques to customize package installation locations:

• Using download.url: Some R packages provide a download.url argument that allows you to specify the download URL for the package. You can then use this URL to install the package using devtools::install_github().
• Creating Custom Install Scripts: If you need more control over package installation locations, you can create custom install scripts using R’s shell scripting capabilities.
• Using .R/Makefile Files: By creating a .R/Makefile file within your working directory and specifying the PKGFOLDER environment variable, you can customize where packages are installed.

In conclusion, while devtools::install_github() provides an easy way to install packages from GitHub repositories, it doesn’t offer as much control over package installation locations as other tools. Nevertheless, there are ways to work around these limitations and achieve the desired results.

Additional Resources

For more information on how to use devtools in R, check out these resources:

• DevTools
• RStudio Documentation
• R Package Development

Last modified on 2024-04-23