solutions session 6

Exercises 3

Practice finding the right selector with the CSS Diner game: https://flukeout.github.io/
Consider the toy HTML example below. Which selectors do you need to put into html_elements() (which extracts all elements matching the selector) to extract the information

library(rvest)
webpage <- "<html>
<body>
  <h1>Computational Research in the Post-API Age</h1>
  <div class='author'>Deen Freelon</div>
  <div>Keywords:
    <ul>
      <li>API</li>
      <li>computational</li>
      <li>Facebook</li>
    </ul>
  </div>
  <div class='text'>
    <p>Three pieces of advice on whether and how to scrape from Dan Freelon</p>
  </div>
  
  <ol class='advice'>
    <li id='one'> use authorized methods whenever possible </li>
    <li id='two'> do not confuse terms of service compliance with data protection </li>
    <li id='three'> understand the risks of violating terms of service </li>
  </ol>

</body>
</html>" |>
  read_html()

# the headline
headline <- html_elements(webpage, "h1")
headline
# the author
author <- html_elements(webpage, ".author")
author
# the ordered list
ordered_list <- html_elements(webpage, "ol")
ordered_list
# all bullet points
bullet_points <- html_elements(webpage, "li")
bullet_points
# bullet points in unordered list
bullet_points_unordered <- html_elements(webpage, "ul li")
bullet_points_unordered
# elements in ordered list
bullet_points_ordered <- html_elements(webpage, "ol *")
bullet_points_ordered
# third bullet point in ordered list
bullet_point_three_ordered <- html_elements(webpage, "#three")
bullet_point_three_ordered
# alternativ
bullet_point_three_ordered <- html_elements(webpage, "ol li:nth-child(3)")
bullet_point_three_ordered