5.7 R packages & access

• Either use suitable R package or write API call yourself
• Always check whether there is an R package that you could use!
  • CRAN Web Technologies Task View (but only packages released in CRAN)
  • GitHub (including unreleased packages and most recent versions of packages)
  • e.g., deeplr
  • rOpenSci Consortium
• httr package: Tools for Working with URLs and HTTP (and write API calls)
  • GET(url = NULL,query=(xxx=xxx), ...): GET something from server (e.g., GET("http://httpbin.org/get"))
  • POST(): POST something to server (e.g., POST("http://httpbin.org/post", body = "this is a test"))
  • content(): Extract content from a request
    • content(GET("https://wikimedia.org/api/rest_v1/metrics/pageviews/per-article/en.wikipedia.org/all-access/all-agents/Hadley_Wickham/daily/20170101/20170102"))
    • content(response, type = "text"): Override server content type with type = "text"
• Status codes: 200 (success!), 4XX (client error), 5XX (server error)