3 R functions that I enjoy

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Straight from my sticky note, three functions that I like a lot, despite their not being new at all… But maybe new to some of you?

sprintf(), the dependency-free but less neat “glue”

Imagine I want to tell you who I am.

I could write

name <- whoami::fullname()
github_username <- whoami::gh_username()
glue::glue("My name is {name} and you'll find me on GitHub as {github_username}!")
#> My name is Maëlle Salmon and you'll find me on GitHub as maelle!

(Maybe the whoami package by Gábor Csárdi is a sub topic of this section?! So handy!)

The code above is very readable. The nice syntax with curly braces is something one finds again in the cli package.1

Now, there’s a dependency-free version of the glue code! Albeit a bit uglier 🤐

name <- whoami::fullname()
github_username <- whoami::gh_username()
  "My name is %s and you'll find me on GitHub as %s!",
#> [1] "My name is Maëlle Salmon and you'll find me on GitHub as maelle!"

Sure it’s less readable, since the replacements are identified by their position, but I often find myself using it! I clearly remember seeing it in other people’s code and wondering what that was.

It’s a pattern one finds in other languages: the manual page for the function states “Use C-style String Formatting Commands”, and I know the Hugo equivalent.

append() and its after argument

To append values to a vector, I mostly use c(), but I recently discovered the base R function append() and its after argument that indicates where to include the new values! By default, the values are appended at the end of the vector.

I most recently used append() to create a test fixture.

x <- c("thing", "stuff", "element")
values <- c("bla", "blop")
append(x, values)
#> [1] "thing"   "stuff"   "element" "bla"     "blop"
append(x, values, after = 2)
#> [1] "thing"   "stuff"   "bla"     "blop"    "element"

It’s not a function I use every day, but it can come in handy depending on what you’re doing!

For my fellow XML fans out there, it reminds me of the .where argument of xml2::xml_add_sibling() and xml2::xml_add_child().

servr::httw() to serve a local directory as a website

Do you know about the servr package by Yihui Xie?

Its use case is having a local directory that is the source of a website, and wanting to preview it locally in your browser as if it were served by a real server.

I make use of it when working on the babelquarto package for instance, that builds multilingual Quarto books or websites. In the code of the multilingual books/websites, links to the other language versions are relative so they don’t work if I simply open HTML files in my browser. So, instead, I write servr::httw(<directory-with-the-website-source>).

You can also use servr if you want to preview locally your pkgdown website and be able to use the search function.

There’s servr::httw() that watches changes in the directory, and the more simple servr::httd().


Today I shared about sprintf() for glue-like functionality, append() and its after argument for appending values where you want in a vector, and servr::httw() for serving static files.

  1. Curious about cli? Come to this cool rOpenSci coworking session next week! ↩︎

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