FILEPATH
Returns the file directory as a string.
info
Remember to escape the backslashes in your file path, otherwise your expression will error.
Syntax
string FILEPATH(string fileName)
Example
FILEPATH("C:\mydir\myfile.ext")
Will return 'C:\mydir'.
If you have a series of documents contained within folders for example the structure might be : Documents\Folder1\Document1.docx
you could pass the Path column into the function:
FILEPATH(Path)
This would return Documents
as the result as that is the first directory the document is stored in.