How can I get R to follow symbolic links in Windows 10? - r

Question

I have multiple RStudio projects, each in its own working directory. All of the projects draw data from the same series of CSV files.
I would like to place the CSV files in a separate "data" directory, then put a Windows shortcut inside each project directory pointing to the data directory. The directory structure would thus be:
/data
/project-1
/project-1/data = Windows shortcut pointing to /data
/project-2
/project-2/data = Windows shortcut pointing to /data
etc.
However, when I attempt to access the "data" directory via the shortcut from e.g. project-1, R generates the following error:
> write.csv(df, "data/df.csv")
Error in file(file, ifelse(append, "a", "w")) :
cannot open the connection
In addition: Warning message:
In file(file, ifelse(append, "a", "w")) :
cannot open file 'data/df.csv': No such file or directory
What am I doing wrong?

Answer 1

I didn't know this, because I've spent the past 10 years using Linux instead of Windows, but:
In Windows, "shortcuts" are not symbolic links. To create an actual symbolic link, you have to open a command prompt as administrator (!?! - or activate developer mode) then create a link using mklink. RStudio does correctly follow symbolic links created that way.
Sadly, Windows Explorer does not correctly follow symbolic links created that way. And you can't create hard links to directories. So either way, it is only half functional. Bloody Windows.

Answer 2

I know this is an old question but solution was never posted.
Solution:
Create a soft link in windows.
To do that, open command line as and admin.
use "mklink" command. The best approach is to use full path to both locations.
mklink works like this:
mklink LinkLocation PathToFile
If you want to do directory use "/D".
For example: "mklink /D C:\myNewLink F:\LocationOfMyDirectorry
Such links should work in R with no trouble (like regular folder/file).
Important to add that soft link can point to soft link :D

Answer 3

Nice thinking! I actually had a similar idea not too long ago: the use of Windows shortcuts (.lnks) would let one refer to resources without redundancy, and seamlessly point (or redirect) to various locations...all with a few mouse-clicks in Windows File Explorer!
Where You Went Wrong
Consider this situation for /project-1. When you create a shortcut (to /data) within the /project-1 directory, you are not creating a subdirectory named data
.
├── project-1.Rproj
├── data # A subdirectory.
│ └── …
└── …
but rather a shortcut (.lnk) file named data:
.
├── project-1.Rproj
├── data.lnk # A shortcut.
└── …
As such, R
cannot open file 'data/df.csv'
because the ./data directory does not exist under /project-1:
No such file or directory
Solutions
For my own project, my search turned up two lifesaving packages: fs (in the tidyverse) and R.utils.
Now fs does have the benefit of stability and consistency with the tidyverse. It provides a standardized interface to create symbolic links, and its fs::link_path() will let you read those links.
🚨🚨🚨 However, Windows shortcuts are NOT symbolic links. 🚨🚨🚨
As such, I much prefer the superior power and relevance of R.utils::filePath(). For one thing, it can actually expand Windows shortcuts (.lnks) specifically. For another, it will let you treat the shortcut to a directory as a directory:
# Refers to 'data.lnk' shortcut ↴
# |--|
R.utils::filePath("./project-1/data")
#> "/data"
# Refers to 'data.lnk' shortcut ↴
# |--|
R.utils::filePath("./project-1/data/my_data.csv")
#> "/data/my_data.csv"
Indeed, you can chain together an arbitrary number of such shortcuts by name, as if they were directories! That is, given a structure like
# Current working directory.
.
| # Shortcut (named 'd2') to a directory.
├── d2.lnk |►───┐
└── … |
|
|
path/to/dir_2 ◄─┘
├── subdir
| | # Shortcut (named 'd3') to a directory.
│ ├── d3.lnk |►─┐
| └── … |
└── … |
|
|
path/to/dir_3 ◄───┘
| # Normal CSV file.
├── foo.csv
| # Shortcut (named 'bar') to a file.
├── bar.lnk |►─────────┐
└── … |
|
|
path/to/dir_4 |
| # Normal text file. |
├── qux.txt ◄──────────┘
└── …
you can "unwrap" the paths to foo.csv and qux.txt like so:
R.utils::filePath("./d2/subdir/d3")
#> "path/to/dir_3"
R.utils::filePath("./d2/subdir/d3/foo.csv")
#> "path/to/dir_3/foo.csv"
# No '.lnk' extension needed ↴
R.utils::filePath("./d2/subdir/d3/bar")
#> "path/to/dir_4/qux.txt"