Import JSON file from URL into R

Question

I've been trying to import a JSON file into R for a while using both the rjson and RJSONIO package, but I can't get it to work. One of the variations of code I used:

json_file <- "http://toolserver.org/~emw/index.php?c=rawdata&m=get_traffic_data&p1=USA&project1=en&from=12/10/2007&to=4/1/2011"
json_data <- fromJSON(paste(readLines(json_file), collapse=""))

This results in an error message:

Error in fromJSON(paste(readLines(json_file), collapse = "")) : 
unexpected character '<'

I think the problem is in the first line of code, because json_file contains the source of the website, not the actual content. I've tried getURL() and getURLContent(), but without any success. Any help would be much appreciated!

Edit: as pointed out by Martin Morgan, the problem seems to be with the URL, not the code!

When I visit the url in my browser and view the page source, it is pure HTML, with no JSON. So — Martin Morgan
– Martin Morgan, Commented Sep 25, 2011 at 14:31
Thanks for checking! You're right, but what is displayed on the page is JSON. Do you know of a way to grab that? I've tried some functions in the RCurl package, but without any luck so far. — Steph
– Steph, Commented Sep 25, 2011 at 16:45
Previously, typing the URL into the browser would generate a blank page and fromJSON(json_file) would error as you indicate. Just now, the browser displays JSON, and library(RJSONIO); fromJSON(json_file) works as expected. It seems like the service is not behaving consistently, either because of an issue on 'their' end or because it is meant to be invoked in a more subtle way than just pointing at a URL — Martin Morgan
– Martin Morgan, Commented Sep 25, 2011 at 17:06
Oh wow, it does work with this URL! I'll contact the owner of the tool. Thanks so much for following up! — Steph
– Steph, Commented Sep 25, 2011 at 18:40

Patrick McCann · Accepted Answer · 2012-01-11 20:35:02Z

4

library(rjson)
fromJSON(readLines('http://toolserver.org/~emw/index.php?c=rawdata&m=get_traffic_data&p1=USA&project1=en&from=12/10/2007&to=4/1/2011')[1])

works for me, with a warning

answered Jan 11, 2012 at 20:35

Patrick McCann

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