15 · Channels II — scraping

Thursday, Oct 15, 2026

Materials for this session are not published yet. They appear here before class.

Objectives

By the end of this session you can:

• Target page elements with CSS selectors.
• Scrape politely and legally.
• Catch silent pagination truncation.
• Choose between scraping, an API, and buying the data.

What we cover

• What scraping has measured: prices, job postings, housing listings — data nobody packaged.
• rvest and CSS selectors.
• Politeness: robots.txt, delays, identifying yourself.
• Pagination’s silent failures; snapshot the HTML you scraped.
• When scraping is the wrong tool: an API existed, or the terms forbid it.

Verification habit. Check expected counts — and spot-check the last item, not the first.