3.3 Radian

Q: There is no syntax highlighting in the R terminal. How to fix it?
A: Install Radian, an improved R console REPL interface that corrects many limitations of the official R terminal and supports many features such as syntax highlighting and auto-completion.

Q: How to install Radian?
A: In the terminal, run

$pipx install radian
  installed package radian 0.6.15, installed using Python 3.13.5
  These apps are now globally available
    - radian
⚠️  Note: '/Users/menghan/.local/bin' is not on your PATH environment variable. These apps will not be globally
    accessible until your PATH is updated. Run `pipx ensurepath` to automatically add it, or manually modify your PATH in
    your shell's config file (e.g. ~/.bashrc).
done! ✨ 🌟 ✨

$pipx ensurepath

/Users/menghan/.local/bin has been been added to PATH, but you need to open a new terminal or re-login for this PATH
    change to take effect. Alternatively, you can source your shell's config file with e.g. 'source ~/.bashrc'.

You will need to open a new terminal or re-login for the PATH changes to take effect. Alternatively, you can source your
shell's config file with e.g. 'source ~/.bashrc'.

N.B. If you have zsh as your shell, you need to run source ~/.zshrc instead of source ~/.bashrc.

To find where radian is installed, you can run:

which radian
/Users/menghan/.local/bin/radian

This is the path to the radian executable.

After adding Radian to your PATH, you can invoke it in the terminal by simply typing radian.

$radian
R version 4.3.1 (2023-06-16) -- "Beagle Scouts"
Platform: aarch64-apple-darwin20 (64-bit)

r$>

Then, in VS Code, you will need to set Radian as the default R terminal. You can also configure other settings for R.

Add the following settings to your settings.json file:

{
  /* R settings */ 
  "r.rterm.mac": "/Users/menghan/.local/bin/radian",
  "r.bracketedPaste": true,
  "r.sessionWatcher": true,
  "r.plot.useHttpgd": true,
  "[r]": {
    "editor.defaultFormatter": "REditorSupport.r",
    "editor.formatOnType": true
  },
  "r.formatting.style": "styler",
}

Options:

  • r.rterm.mac: Path to the Radian executable.

  • r.bracketedPaste: Enables bracketed paste mode, which allows pasting code without executing it immediately. This is useful if you want to paste multiple lines of code into the console at once.

  • r.sessionWatcher: Enables session watcher to monitor the R session. Specifically,

    • Show value of session symbols on hover
    • Show plot output on update and plot history
    • Show htmlwidgets, documentation and shiny apps in WebView

  • r.alwaysUseActiveTerminal: always send code to active terminal rather than vscode-R; helps me to start an R session which is terminated when VSCode exits.

  • r.plot.useHttpgd: Use the httpgd package for viewing plots in a VS Code window or in the browser.

  • Language-specific editor settings for R files:

    Prerequisite: install styler package in R.

    install.packages("styler")

    Use styler for code formatting, and set the default formatter to REditorSupport.r.

    REditorSupport.r and styler are able to identify specific R syntax, e.g., %>% and |> as pipe operators, and will format the code accordingly. By contrast, the default formater in VS Code does not recognize these operators and fails to auto indent after a pipe operator.

    "editor.formatOnType": true will trigger formatting as you type.

See Extension Settings for a full list of settings of vscode-R that can be set in VSCode’s settings.json file.

3.3.1 Configuration

Radian can be customized by specifying the below options in various locations:

  • $HOME/.config/radian/profile
  • .radian_profile in the working directory

Example of a radian profile

# either  `"emacs"` (default) or `"vi"`.
options(radian.editing_mode = "vi")

# enable various emacs bindings in vi insert mode
options(radian.emacs_bindings_in_vi_insert_mode = TRUE)

# show vi mode state when radian.editing_mode is `vi`
options(radian.show_vi_mode_prompt = TRUE)
options(radian.vi_mode_prompt = "\033[0;34m[{}]\033[0m ")

# custom key bindings
options(
    radian.escape_key_map = list(
        list(key = "-", value = " <- "),
    ),
    radian.ctrl_key_map = list(
        list(key = "p", value = " %>% ")
    )
)

  • Insert pipe operator %>% by pressing Ctrl + P

  • Insert assignment operator <- by pressing Esc + -

    But this does not work when Vim is enabled as it interferes with Vim’s normal mode.

VI support by radian:

  • options(radian.editing_mode = "vi"): set the default editing mode to vi.

  • options(radian.show_vi_mode_prompt = TRUE): This option will show the current vi mode in the prompt when using radian in vi mode. The prompt will be colored blue and will display the current mode.

    • [ins]: insert mode
    • [nav]: normal mode

Q: How to restart Radian?
A: Run rstudioapi::restartSession() in the R terminal.

You can define a function to restart Radian.

In .Rprofile, add the following function definition:

# restart function, convenient in radian
restart <- function() {
    getOption("rchitect.py_tools")$attach()
    os <- import("os")
    sys <- import("sys")
    os$execv(sys$executable, c("sys$executable", "-m", "radian"))
}

This snippet use Python to use os.execv() to replace the current process with a new instance of Radian. When you call restart(), it will effectively restart Radian without needing to close and reopen the terminal manually.

This is more robust than rstudioapi::restartSession().

Issue: the restart() function, cannot use rstudioapi:: functions.

Workaround: Close R and create a new R terminal manually or use rstudioapi::restartSession().

3.3.2 Data Viewer

You can view objects in the workspace by clicking the R icon in the Activity bar. It is a convenient way to view the R workspace, preview existing R objects, find help topics, and read help pages interactively.

You can use view() to open the data viewer in a new tab. For example, view(mtcars) will open the mtcars dataset in the data viewer.