Change path.expand location (Win 7)

To persistently reset the directory that "~" resolves to for all users, put the following in the file Renviron.site, located in $RHOME/etc/Renviron.site:

R_USER="C:/Users/trinker"

(If the file is not already there, you can just create it yourself.)

If a computer supports multiple R users, and each wants to set their own R_USER location, each can put the following in their own ".Rprofile" file:

Sys.setenv(R_USER = "C:/Users/trinker")

".Rprofile" is looked for in the user's home directory, which is returned by typing Sys.getenv("HOME"). See ?Startup and the R for Windows FAQ for more details.

(Thanks to @Dason for pointing out the .Rprofile option.)