How to scrape the web for the list of R release dates?

Question

To celebrate the 20,000th question with the r-tag on Stack Overflow, please help me to extract the R release dates from the Wikipedia page.

My attempts:

library(XML) x <- readHTMLTable("http://en.wikipedia.org/wiki/R_(programming_language)") 

This doesn't work because the table is in fact a list, not an HTML table.

library(httr) x <- GET("http://en.wikipedia.org/wiki/R_(programming_language)") text <- content(x, "parsed") 

This extracts the text, but my xpath is rusty, so I couldn't extract the relevant release dates.

How can I do this?

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PS. The Wikipedia page is the only source I could find, but please feel free to post a solution using canonical source, if there is one.

Answer 1

Why don't you use the file dates on the canonical ftp archive in Vienna?

Edit: Eg

 lynx -dump http://cran.r-project.org/src/base/R-0/ | grep tgz | grep -v http 

gets you a table you can parse from R. Gets you file sizes as a benefit. Rinse and repeat for R-1 and R-2 directories.

Answer 2

Edited to include R version 3.0.0 and above

Dirk Eddelbuettel provided the canonical link to the .0 releases of R.

Here is some code that collates the tables from the three separate URLs, one for each major release, and then plot it:

library(XML) library(lattice)   getRdates <- function(){   url <- paste0("http://cran.r-project.org/src/base/R-", 0:3)   x <- lapply(url, function(x)readHTMLTable(x, stringsAsFactors=FALSE)[[1]])   x <- do.call(rbind, x)   x <- x[grep("R-(.*)(\\.tar\\.gz|\\.tgz)", x$Name), c(-1, -5)]   x$Release <- gsub("(R-.*)\\.(tar\\.gz|tgz)", "\\1", x$Name)   x$Date <- as.POSIXct(x[["Last modified"]], format="%d-%b-%Y %H:%M")   x$Release <- reorder(x$Release, x$Date)   x }  x <- getRdates() dotplot(Release~Date, data=x)