[Rd] How is the environment variable "R_USER" defined?

[Jiefei Wang]

Hi, I have a new win system and try to install R as usual. Somehow,
the environment variable "R_LIBS_USER" is incorrectly pointed to a
Onedrive folder. Since "R_LIBS_USER" depends on "R_USER", the root
problem then becomes why "R_USER" is the path to the Onedrive. I did
an exhausting search in the R directory and the only related message I
can find is from EnvVar.html, which states

R_USER: The user's ‘home’ directory. Set by R. (HOME will be set to
the same value if not already set.)

I guess that's another way to say "no document is available yet". I
also took a look at my system environment variables but there are only
two variables related to Onedrive, they are

OneDrive=C:\Users\wangj\OneDrive

OneDriveConsumer=C:\Users\wangj\OneDrive

so everything looks pretty normal, I know I can correct this issue by
manually adding Renviron but I just wonder where this default behavior
comes from...

Best,
Jiefei