Case study: Compare package versions on CRAN and GitHub

compare_versions.R

library(RCurl)
library(magrittr)
library(stringr)

compare_versions <- function(package) {
  cranurl <- paste("https://cran.r-project.org/web/packages/", package, "/", sep = "")
  cranfile <- getURL(cranurl)
  cranversion <- cranfile %>% 
    str_extract("(?<=Version:</td>\n<td>)[0-9a-zA-Z.-]*")
  ghurl <- cranfile %>% 
    str_extract('(?<=URL:</td>\n<td>).*') %>%
    str_extract("(?<=>).*") %>%
    str_extract('(.*?)(?=<)')
  ghversion <- ghurl %>%
    str_extract("(?<=.com/).*") %>%
    paste("https://raw.githubusercontent.com/", . , "/master/DESCRIPTION", sep = "") %>%
    getURL() %>%
    str_extract("(?<=Version: ).*")
  table <- data.frame(cranversion, ghversion, stringsAsFactors = F) %>%
    `colnames<-`(c("CRAN Version", "GitHub Version"))
  return(table)
}