How do I check the existence of a downloaded file

r

Solution

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") 
}

Problem

I've created a R markdown file that starts by loading a file from the web. I found the cache=TRUE to be a little flaky so I want to put an if condition in to check for the downloaded file before downloading it. Current Code - Always downloads file ``` fileURL <- "https://dl.dropbox.com/u/7710864/courseraPublic/samsungData.rda" setInternet2(TRUE) download.file(fileURL ,destfile="./data/samsungData.rda",method="auto") load("./data/samsungData.rda") ``` Desired Code - only upload if if not already downloaded ``` destfile="./data/samsungData.rda" fileURL <- "https://dl.dropbox.com/u/7710864/courseraPublic/samsungData.rda" if (destFile doesNotExist) { setInternet2(TRUE) download.file(fileURL ,destfile,method="auto") } load("./data/samsungData.rda") } load(destfile) ``` What syntax will give me the condition "destFile doesNotExist"

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