R extension write local data

Question

I am creating a package and would like to store settings data locally, since it is unique for each user of the package and so that the setting does not have to be set each time the package is loaded.

How can I do this in the best way?

Answer 1

You could save your necessary data in an object and save it using saveRDS() whenever a change it made or when user is leaving or giving command for saving. It saves the R object as it is under a file name in the specified path.

saveRDS(<obj>, "path/to/filename.rds")

And you can load it next time when package is starting using loadRDS(). The good thing of loadRDS() is that you can assign a new name to the obj. (So you don't have to remember its old obj name. However the old obj name is also loaded with the object and will eventually pollute your namespace.

newly.assigned.name <- loadRDS("path/to/filename.rds")
# or also possible:
loadRDS("path/to/filename.rds") # and use its old name

Where to store

Windows

Maybe here:

You can use %systemdrive%%homepath% environment variable to accomplish this.

The two command variables when concatenated gives you the desired user's home directory path as below:

Running echo %systemdrive% on command prompt gives:

C:

Running echo %homepath% on command prompt gives:

\Users\

When used together it becomes:

C:\Users\

Linux/OsX

Either in the package location of the user,

path.to.package <- find.package("name.of.your.pacakge", 
                                lib.loc = NULL, quiet = FALSE,
                                 verbose = getOption("verbose"))
# and then construct with 
destination.folder.path <- file.path(path.to.package, 
                                     "subfoldername", "filename")`
# the path to the final destination
# You should use `file.path()` to construct such paths, because it detects automatically the correct ('/' or '\') separators for the file paths in Unix-derived systems (Linux/Mac Os X) versus Windows.

Or use the $HOME variable of the user and there in a file - the name of which beginning with "." - this is convention in Unix-systems (Linux/Mac OS X) for such kind of file which save configurations of software programs. e.g. ".your-packages-name.rds".

If anybody has a better solution, please help!