How do I check the existence of a downloaded file

Solution 1:

You can use tryCatch

  if(!file.exists(destfile)){
    res <- tryCatch(download.file(fileURL,
                              destfile="./data/samsungData.rda",
                              method="auto"),
                error=function(e) 1)
    if(dat!=1) load("./data/samsungData.rda") 
}

Solution 2:

As per the answer given by @agstudy

 destfile="./data/samsungData.rda" 
 fileURL <-
 "https://dl.dropbox.com/u/7710864/courseraPublic/samsungData.rda"   
 if (!file.exists(destfile)) {
    setInternet2(TRUE)
    download.file(fileURL ,destfile,method="auto") }
    load("./data/samsungData.rda")
 }
 load(destfile)