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As Wikipedia says, “lint, or a linter, is a tool that analyses source code to flag programming errors, bugs, stylistic errors, and suspicious constructs.” In other words, linting is the process of standardising the format of how your code looks.

All written work has rules, either official or unofficial, about how it should be formatted. If you pick up and read a report you can expect a cover page, contents page, sections with headings in bold, page numbers, etc. Something like a thesis will additionally have chapters and appendices, and its bibliography will always follow the strict formatting rules of whichever referencing style it uses. In the same way, someone reading your code will have certain expectations about its format, and if your code is all over the place it will reduce its readability. This is why code style is important.

# 1 Examples of Linting Errors

Trailing whitespace is superfluous:

# Bad:
print("Hello, World") ↵
# Good:
print("Hello, World")

Lines should not be more than 80 characters:

# Bad:
print(ifelse(variable == 78, sprintf("This is a long line %s", variable), "Avoid this"))
# Good:
print(
ifelse(
variable == 78, sprintf("This is a long line %s", variable),
"But it is broken up so it is fine"
)
)

Commented code should be removed:

# bad <- TRUE
good <- TRUE

Do not place spaces around code in parentheses or square brackets:

# Bad:
print( "Hello, World" )
# Good:
print("Hello, World")

Put spaces around all infix operators:

# Bad:
2+2
# Good:
2 + 2

Use <- not = for assignment:

# Bad:
x = 2 + 2
# Good:
x <- 2 + 2

Variable and function name style should be snake_case:

ThisIsBad <- 5
this_is_good <- 5

# 2 How It Used To Be Done

In the old days, coders would use style guides (such as this one or this one or this one, and before the internet was what it is today the might even have used actual, physical books) in order to look up how to manually format their code. Fortunately, these days we have packages to do this for us, so take a look below:

# 3 The Lintr Package

This package will import an R script (or an R Markdown script that contains R code) and search it for style errors. Then it will tell you what they are so that you can fix them. To get it working do one of the following:

In RStudio:

• Install the package:
• Manually: select the “Packages” tab in the lower right-hand-side section > Install > search for “lintr” in the “Packages” search bar > Install
• Programmatically: run install.packages("lintr") in the Console
• Point to the correct folder: use setwd() in the console to change to the folder where your script is
• Run the linter manually:
lint("<your_filename>.R>")

In the Terminal:

• Install the package:
• Open R by running R > run install.packages("lintr") > run q() to quit
• Point to the correct folder:
• Use cd to move into the folder where your script is
• Run the linter manually:
• Open R by running R
• Run:
library(lintr)
lint("<your_filename>.R>")

This will produce an output showing the linting errors in your file. Ideally, nothing will be produced. For more information see the docs.

## 3.1 Integrating the Linter with RStudio

You can bind this linting process to a keyboard shortcut in RStudio to make it as easy for yourself as possible:

• Enable the “Markers” pane in RStudio: from the menu bar > “Tools” > “Global Options…” > go to “Code” on the left-hand-side > “Diagnostics” tab > check “Show diagnostics for R”
• Create a keybinding: “Tools” > “addins” > “Browse Addins…” > “Keyboard Shortcuts…” > click in the “Shortcut” column next to “Lint current file” and press your desired key combination
• It’s recommended to use Shift+Alt+L on Linux/Windows or Shift+Alt+Cmd+L on macOS

## 3.2 Integrating the Linter with Sublime Text

lintr can be used with Sublime Linter for on-the-fly linting:

• Install SublimeLinter using Package Control
• Try install sublimeLinter-contrib-lintr using Package Control. If this doesn’t work then do it manually:
• Sublime Text > Preferences > Browse Packages…
• A folder will open. Place the unzipped folder in here.

Optionally, you can configure what linters are used or what specific linting rules are used. For example, you can have a different line length cutoff by changing the SublimeLinter User Settings to the following:

{
"user": {
"linters": {
"r": {
"linters": "with_defaults(line_length_linter(120))"
}
}
}
}

# 4 The Styler Package

This will take things one step further than the lintr package in that it will actually make the linting changes it suggests.

• Install the styler package in the same way as was detailed above for the lintr package
• Use it in a similar way as the lintr package as well, although this time the R code to run is:
library(styler)
writeLines(style_text(input), con = "<your_filename>.R")