The R client for Sage Synapse works transparently with R data files. Using other types of files requires a bit more work. Here's a short demonstration of how to do it.

load_synapse_data_file.R

## Loading with files in the R synapse client
##################################################

## If you haven't already, install the synapse R client
# source('http://depot.sagebase.org/CRAN.R')
# pkgInstall(c("synapseClient"))

library(synapseClient)

## list the files in a project
synapseQuery('select id,name from entity where parentId=="syn1661878"')
# entity.name  entity.id
# 1                data.txt syn1661879
# 2 generate_random_data.py syn1661881
# 3               square.py syn1661884
# 4             squares.txt syn1661886

## let's get data.txt, which happens to be a text file holding a bunch
## of floating point numbers
e <- loadEntity('syn1661879')

## list the files
e@objOwn$objects@fileCache$files()
# [1] "data.txt"

## paste together the filename(s)
filename <- paste(e@objOwn$objects@fileCache$getCacheDir(), e@objOwn$objects@fileCache$files(), sep="/" )

## read the data with the method appropriate to the file type,
## in this case a simple scan will do. Otherwise, try read.delim
## or read.csv.
data <- scan(file=filename)

Loading the data is format specific. The call to scan might be replaced by read.table, read.csv or something else, depending on the type of data in the file.