How to download an .xlsx file from a dropbox (https:) location - r

Question

I'm trying to adopt the Reproducible Research paradigm but meet people who like looking at Excel rather than text data files half way, by using Dropbox to host Excel files which I can then access using the .xlsx package.
Rather like downloading and unpacking a zipped file I assumed something like the following would work:
# Prerequisites
require("xlsx")
require("ggplot2")
require("repmis")
require("devtools")
require("RCurl")
# Downloading data from Dropbox location
link <- paste0(
"https://www.dropbox.com/s/",
"{THE SHA-1 KEY}",
"{THE FILE NAME}"
)
url <- getURL(link)
temp <- tempfile()
download.file(url, temp)
However, I get Error in download.file(url, temp) : unsupported URL scheme
Is there an alternative to download.file that will accept this URL scheme?
Thanks,
Jon

Answer 1

You have the wrong URL - the one you are using just goes to the landing page. I think the actual download URL is different, I managed to get it sort of working using the below.
I actually don't think you need to use RCurl or the getURL() function, and I think you were leaving out some relatively important /'s in your previous formulation.
Try the following:
link <- paste("https://dl.dropboxusercontent.com/s",
"{THE SHA-1 KEY}",
"{THE FILE NAME}",
sep="/")
download.file(url=link,destfile="your.destination.xlsx")
closeAllConnections()

Answer 2

UPDATE:
I just realised there is a source_XlsxData function in the repmis package, which in theory should do the job perfectly.
Also the function below works some of the time but not others, and appears to get stuck at the GET line. So, a better solution would be very welcome.
I decided to try taking a step back and figure out how to download a raw file from a secure (https) url. I adapted (butchered?) the source_url function in devtools to produce the following:
download_file_url <- function (
url,
outfile,
..., sha1 = NULL)
{
require(RCurl)
require(devtools)
require(repmis)
require(httr)
require(digest)
stopifnot(is.character(url), length(url) == 1)
filetag <- file(outfile, "wb")
request <- GET(url)
stop_for_status(request)
writeBin(content(request, type = "raw"), filetag)
close(filetag)
}
This seems to work for producing local versions of binary files - Excel included. Nicer, neater, smarter improvements in this gratefully received.