Writing code for R packages

The first principle of using a package is that all R code goes in R/. In this lesson, you’ll learn about the R/ directory, my recommendations for organizing your functions into files, and some general tips on good style. You’ll also learn about some important differences between functions in scripts and functions in packages.

R Code Workflow

The first practical advantage to using a package is that it’s easy to reload your code. You can either run devtools::load_all(), or in RStudio press Ctrl/Cmd-Shift-L, which also saves all open files, saving you a keystroke.

This keyboard shortcut leads to a fluid development workflow:

1. Edit an R file.

2. Press Ctrl/Cmd-Shift-L.

3. Explore the code in the console.

4. Rinse and repeat.

Congratulations! You’ve learned your first package development workflow. Even if you learn nothing else from this book, you’ll have gained a useful workflow for editing and reloading R code.

Organizing Your Functions

While you’re free to arrange functions into files as you wish, the two extremes are bad: don’t put all functions into one file and don’t put each function into its own separate file. (It’s OK if some files only contain one function, particularly if the function is large or has a lot of documentation.) Filenames should be meaningful and end in .R:

# Good
fit_models.R
utility_functions.R

# Bad
foo.r
stuff.r

Pay attention to capitalization, because you, or some of your collaborators, might be using an operating system ...