CODEWITHSUNDEEP
r
user1605665
user1605665

Reputation: 4151

How do I check the existence of a downloaded file

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"

Upvotes: 76

Views: 98922

Answers (3)

Nutan
Nutan

Reputation: 340

An easy way to check the existence of a file in your working directory is: which(list.files() == "nameoffile.csv")

This doesn't exactly answer his question but I thought this might be helpful to someone who simply wants to check if a particular file is there in their directory.

Upvotes: 12

user1605665
user1605665

Reputation: 4151

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)

Upvotes: 26

agstudy
agstudy

Reputation: 121568

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") 
}

Upvotes: 82

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