> library(twitteR)
> cred <- getTwitterOAuth("ikzCtYif9Rwoood45w","rsCCifp99kw5sJfKfOUhhwyVmPl9A")
> registerTwitterOAuth(cred)
[1] TRUE
> T <- userTimeline('freakonometrics',n=5000)

To enable the connection, please direct your web browser to:

http://api.twitter.com/oauth/authorize?oauth_token=cQaDmxGe...

When complete, record the PIN given to you and provide it here:

> T <- userTimeline('freakonometrics',n=5000)

Now, my (third) problem was to extract from my tweets the url of references. The second tweet of the list was

• [textmining] “How a Computer Program Helped Reveal J. K. Rowling as Author of A Cuckoo’s Calling” scientificamerican.com/article.cfm?id… by @garethideas
  

But when you look at the text, you see

> extraire <- function(entree,motif){
+	res <- regexec(motif,entree)
+	if(length(res[[1]])==2){
+		debut <- (res[[1]])[2]
+		fin <- debut+(attr(res[[1]],"match.length"))[2]-1
+		return(substr(entree,debut,fin))
+	}else return(NA)}
> unshorten <- function(url){
+	uri <- getURL(url, header=TRUE, nobody=TRUE, followlocation=FALSE, 
+       cainfo = system.file("CurlSSL", "cacert.pem", package = "RCurl"))
+	res <- try(extraire(uri,"\r\nlocation: (.*?)\r\nserver"))
+	return(res)}

Now, if we use those functions, we can get the true url,

> url <- "http://t.co/wdmBGL8cmj"
> unshorten(url)
[1] http://www.scientificamerican.com/article.cfm?id=how-a-computer-program-helped-show..

> exturl <- function(i){
+ text_tw <- T_text[i]
+ locunshort2 <- NULL
+ indtext <- which(substr(unlist(strsplit(text_tw, " ")),1,4)=="http")
+ if(length(indtext)>0){
+ loc <- unlist(strsplit(text_tw, " "))[indtext]
+ locunshort=unshorten(loc)
+ if(is.na(locunshort)==FALSE){
+ locunshort2 <- unlist(strsplit(locunshort, "/"))[3]}}
+ return(locunshort2)}