Chapter 4 Paths and projects

Learning goals

By the end of this chapter you should be able to:

  • Explain the difference between absolute and relative paths.
  • Use relative paths in your scripts.
  • Use an RStudio Project to keep work organised.

Prerequisites

  • You have installed R and RStudio and created the BB852 folder described in the previous chapter.

A tiny motivating example

If the same project structure is present, this will work on any computer:

read.csv("CourseData/carnivora.csv")

If your project is not organised, you end up with long absolute paths that break when shared.

4.1 File paths in plain language

A file path is the address of a file on your computer. There are two types.

4.1.1 Absolute paths (full address)

These start from the root of your computer:

  • Windows: C:/Users/YourName/Documents/Project/myData.csv
  • macOS: /Users/YourName/Documents/Project/myData.csv

Why this is a problem: Absolute paths often differ between computers, so code containing them may break when it is shared.

4.2 Use an RStudio Project

What we’re about to do: Set a predictable working directory.

An RStudio Project creates a .Rproj file and sets the project folder as the working directory every time you open it.

4.2.1 How to create a project

  1. Use the BB852 folder you created in the previous chapter. If you have not yet created it, do that now.
  2. In RStudio, go to File > New Project.
  3. Choose Existing Directory and select your folder.
  4. Click Create Project.

From now on, open the .Rproj file to work on this course. You do not need to use setwd() in your scripts.

Common mistake: Calling setwd() inside scripts. A path that works on your machine will often fail on somebody else’s.

Takeaway: RStudio Projects keep your paths stable and your work reproducible.

4.3 Suggested folder structure

Keep your project tidy:

  • CourseData/ for data files
  • scripts/ for code
  • plots/ for exported figures
  • writing/ for notes or reports

Try this: Create those folders now (if they do not already exist).

4.4 Key takeaways

  • Relative paths make your code shareable.
  • RStudio Projects set the working directory automatically.
  • A simple folder structure saves time and confusion.

4.5 Common pitfalls recap

  • Using absolute paths in scripts.
  • Using setwd() so that a script depends on a machine-specific location.
  • Saving data and scripts in the same messy folder.

4.6 Try this

Create a new project folder with the structure above, then:

  1. Check that carnivora.csv is in CourseData/.
  2. Import it using read.csv("CourseData/carnivora.csv").
  3. Write one sentence explaining why the relative path is better than the absolute one.