File Systems

In order to read a data set, you need to tell R where it is on your computer.

Your computer's file system is like an upside-down tree.

The root is the beginning: the top of your file system.

The name of the root depends on your operating system and computer:

Each folder or directory beneath the root is a branch of the tree.

Paths

A path is a list of directories that lead to a particular place in a file system. A path can end at a directory or a file.

In a path, directories are separated by forward slashes / rather than commas and spaces.

For example, the file dinosaurs.pdf, in the directory data, in the directory storage, in the root directory:

/storage/data/dinosaurs.pdf

R uses forward slashes in paths regardless of operating system. Outside of R, Windows uses backslashes rather than forward slashes.

If the last part of a path is a directory, you can add a forward slash without changing the meaning.

So we can write:

/storage/data

Or equivalently, we can write:

/storage/data/

The trailing slash helps to disambiguate paths to directories from paths to files.

Website URLs are a more general kind of path:

https://boardgamegeek.com/boardgame/297978/mariposas

The URL has three parts:

If the last part of the path is a directory, you can optionally add a forward slash to the end without changing the meaning:

boardgamegeek.com/boardgame/297978/mariposas/

An absolute path is one that starts from the root directory.

But we can also imagine a path starting from somewhere else in the tree.