Ode to the here package

TL;DR

1. Install here.

   install.packages("here")

2. Use it.

   library(here)
   here("data", "file_i_want.csv")

This works, regardless of where the associated source file lives inside your project. These paths will also “just work” during interactive development, without incessant fiddling with the working directory of your IDE’s R process.

here::here() works like file.path(), but where the path root is implicitly set to "the path to the top-level of my current project". See The Fine Print for the underlying heuristics. If they don't suit, use the more powerful package rprojroot directly. Both here and rprojroot are written by Kirill Müller and are available on CRAN.

Admitting you have a problem

If the first line of your #rstats script is setwd("C:\Users\jenny\path\that\only\I\have"), I will come into your lab and SET YOUR COMPUTER ON FIRE.

Mash-up of rage tweets by @jennybc and @tpoi.

Do you:

• Have setwd() in your scripts? PLEASE STOP DOING THAT.
  • This makes your script very fragile, hard-wired to exactly one time and place. As soon as you rename or move directories, it breaks. Or maybe you get a new computer? Or maybe someone else needs to run your code? We show a very accessible way to go cold turkey and eliminate the setwd() gotcha from your code.
• Fanny around with working directory a lot? During development and/or at run time? YOU CAN STOP DOING THAT TOO.
  • Classic problem presentation: Awkwardness around building paths and/or setting working directory in projects with subdirectories. Especially if you use R Markdown and knitr, which trips up a lot of people with its default behavior of “working directory = directory where this file lives”. We show a very accessible way to specify paths in your project’s .R and .Rmd files, regardless of where they live.

Read my blog post “Project-oriented workflow” for more about why setwd() is so problematic and often associated with other awkward workflow problems. Never fear: there are solutions!

Actual demonstration of here::here()

I will let this code run.

What does here think the top-level of current project is? The package displays this on load or, at any time, you can just call here().

library(here)
#> here() starts at /Users/jenny/rrr/here_here
here()
#> [1] "/Users/jenny/rrr/here_here"

Build a path to something in a subdirectory and use it.

here("one", "two", "awesome.txt")
#> [1] "/Users/jenny/rrr/here_here/one/two/awesome.txt"
cat(readLines(here("one", "two", "awesome.txt")))
#> OMG this is so awesome!

Don’t try this at home, folks! But let me set working directory to a subdirectory and prove to you that the same code as above, for getting the path to awesome.txt, still works.

setwd(here("one"))
getwd()
#> [1] "/Users/jenny/rrr/here_here/one"
cat(readLines(here("one", "two", "awesome.txt")))
#> OMG this is so awesome!

The fine print

here::here() figures out the top-level of your current project using some sane heuristics. It looks at working directory, checks a criterion and, if not satisfied, moves up to parent directory and checks again. Lather, rinse, repeat.

Here are the criteria. The order doesn't really matter because all of them are checked for each directory before moving up to the parent directory:

• Is a file named .here present?
• Is this an RStudio Project? Literally, can I find a file named something like foo.Rproj?
• Is this an R package? Does it have a DESCRIPTION file?
• Is this a remake project? Does it have a file named remake.yml?
• Is this a projectile project? Does it have a file named .projectile?
• Is this a checkout from a version control system? Does it have a directory named .git or .svn? Currently, only Git and Subversion are supported.

If no criteria match, the current working directory will be used as fallback. Use set_here() to create an empty .here file that will stop the search if none of the other criteria apply. dr_here() will attempt to explain why here decided the root location the way it did. See the function reference for more detail.