PL/R is able to pull vectors in from R, though RPostgreSQL cannot pulls
arrays from PostgreSQL as vectors (though it would be great to have this
feature).
I've forgotten how DBI works, but an array should just come through in
form and you can parse it how ever you want on the R side. You can also
send an array by converting it to a string of the appropriate format.
rpg has a 'format_for_send' method that you can dispatch on any type to
convert it to something PostgreSQL can read. I'm working on something for
formatting strings returned from the server.
I've started thinking about a general interface for DBI to do this
too. It's particularly important for SQLite since it has such limited
type information.