rvest: easy web scraping with R

rvest is new package that makes it easy to scrape (or harvest) data from html web pages, inspired by libraries like beautiful soup . It is designed to work with magrittr so that you can express complex operations as elegant pipelines composed of simple, easily understood pieces. Install it with:

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install.packages("rvest")

rvest in action#

To see rvest in action, imagine we’d like to scrape some information about The Lego Movie from IMDB. We start by downloading and parsing the file with html():

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library(rvest)
lego_movie <- html("http://www.imdb.com/title/tt1490017/")

To extract the rating, we start with selectorgadget to figure out which css selector matches the data we want: strong span. (If you haven’t heard of selectorgadget , make sure to read vignette("selectorgadget") - it’s the easiest way to determine which selector extracts the data that you’re interested in.) We use html_node() to find the first node that matches that selector, extract its contents with html_text(), and convert it to numeric with as.numeric():

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lego_movie %>%
  html_node("strong span") %>%
  html_text() %>%
  as.numeric()
#> [1] 7.9

We use a similar process to extract the cast, using html_nodes() to find all nodes that match the selector:

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lego_movie %>%
  html_nodes("#titleCast .itemprop span") %>%
  html_text()
#>  [1] "Will Arnett"     "Elizabeth Banks" "Craig Berry"
#>  [4] "Alison Brie"     "David Burrows"   "Anthony Daniels"
#>  [7] "Charlie Day"     "Amanda Farinos"  "Keith Ferguson"
#> [10] "Will Ferrell"    "Will Forte"      "Dave Franco"
#> [13] "Morgan Freeman"  "Todd Hansen"     "Jonah Hill"

The titles and authors of recent message board postings are stored in a the third table on the page. We can use html_node() and [[ to find it, then coerce it to a data frame with html_table():

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lego_movie %>%
  html_nodes("table") %>%
  .[[3]] %>%
  html_table()
#>                                              X 1            NA
#> 1 this movie is very very deep and philosophical   mrdoctor524
#> 2 This got an 8.0 and Wizard of Oz got an 8.1...  marr-justinm
#> 3                         Discouraging Building?       Laestig
#> 4                              LEGO - the plural      neil-476
#> 5                                 Academy Awards   browncoatjw
#> 6                    what was the funniest part? actionjacksin

Other important functions#

If you prefer, you can use xpath selectors instead of css: html_nodes(doc, xpath = "//table//td")).
Extract the tag names with html_tag(), text with html_text(), a single attribute with html_attr() or all attributes with html_attrs().
Detect and repair text encoding problems with guess_encoding() and repair_encoding().
Navigate around a website as if you’re in a browser with html_session(), jump_to(), follow_link(), back(), and forward(). Extract, modify and submit forms with html_form(), set_values() and submit_form(). (This is still a work in progress, so I’d love your feedback.)