17  Directories and Projects in R

A directory is simply a folder on your computer. R interacts with directories to read data files, write outputs, and organize a project — understanding how to check and set the working directory matters as soon as you start reading a CSV of field data or saving a plot to disk.

17.1 What Is a Working Directory?

The working directory is the default location R reads from and writes to. When you load a file such as field_yields.csv without a full path, R looks for it in the current working directory.

17.2 Checking and Setting the Working Directory

getwd() reports the current working directory; setwd() changes it.

setwd("~/AgriProjects/2026-season-yields")
getwd()   # confirm the change

17.3 Listing Files

list.files() shows what’s available in the current directory — useful for confirming a data file actually exists before trying to read it.

17.4 Best Practices

  • Prefer RStudio Projects over setwd() — creating an .Rproj file (File → New Project) sets the working directory automatically to the project folder whenever it’s opened, which is more reliable than a hard-coded setwd() call that breaks the moment the script moves to another machine or another person’s computer.
  • Use relative, not absolute, paths — "data/field_yields.csv" works on any machine; "/Users/vijay/Library/field_yields.csv" only works on one.
  • Consider the here package for larger projects — here::here("data", "field_yields.csv") builds a path relative to the project root regardless of which subfolder your script happens to run from, which avoids an entire category of “file not found” errors as a project grows.
  • Always confirm with getwd() before reading or saving, especially in a script you’ll hand off to someone else.

Summary

Concept Description
Directories and Projects in R
Working Directory The default folder R reads from and writes to.
Checking and Setting It `getwd()` reports it; `setwd()` changes it.
Listing Files `list.files()` shows what's in the current directory.
Best Practices Prefer RStudio Projects and relative paths (or the `here` package) over hard-coded `setwd()` calls.