Utilisez ceci :
library(RPostgreSQL)
drv <- dbDriver("PostgreSQL")
con <- dbConnect(drv, dbname = "db", host = "host", port = 5432,
user = "user", password = "pwd")
dbWriteTable(con, c("yourschema", "yourtable"), value = yourRdataframe)
dbDisconnect(con)
Plus de détails :https://stat.ethz.ch/pipermail/r-sig-db/2011q1/001043.html