Chapter 3 Practice safe paths

Adapt from https://github.com/jennybc/here_here#readme.

Include some coverage of fs.

3.1 Use projects and the here package

How can you avoid setwd() at the top of every script?

  • Organize each logical project into a folder on your computer.
  • Make sure the top-level folder advertises itself as such. This can be as simple as having an empty file named .here. Or, if you use RStudio and/or Git, those both leave characteristic files behind that will get the job done.
  • Use the here() function from the here package to build the path when you read or write a file. Create paths relative to the top-level directory.
  • Whenever you work on this project, launch the R process from the project’s top-level directory. If you launch R from the shell, cd to the correct folder first.

To continue our example, start R in the foofy directory, wherever that may be. Now the code looks like so:

library(ggplot2)
library(here)

df <- read.delim(here("data", "raw_foofy_data.csv"))
p <- ggplot(df, aes(x, y)) + geom_point()
ggsave(here("figs", "foofy_scatterplot.png"))

This will run, with no edits, for anyone who follows the convention about launching R in the project folder. In fact, it will even work if R’s working directory is anywhere inside the project, i.e. it will work from sub-folders. This plays well with knitr/rmarkdown’s default behavior around working directory and in package development/checking workflows.

Read up on the here package to learn about more features, such as additional ways to mark the top directory and troubleshooting with dr_here(). I have also written a more detailed paean to this package before.