Book Image

R Web Scraping Quick Start Guide

By : Olgun Aydin
Book Image

R Web Scraping Quick Start Guide

By: Olgun Aydin

Overview of this book

Web scraping is a technique to extract data from websites. It simulates the behavior of a website user to turn the website itself into a web service to retrieve or introduce new data. This book gives you all you need to get started with scraping web pages using R programming. You will learn about the rules of RegEx and Xpath, key components for scraping website data. We will show you web scraping techniques, methodologies, and frameworks. With this book's guidance, you will become comfortable with the tools to write and test RegEx and XPath rules. We will focus on examples of dynamic websites for scraping data and how to implement the techniques learned. You will learn how to collect URLs and then create XPath rules for your first web scraping script using rvest library. From the data you collect, you will be able to calculate the statistics and create R plots to visualize them. Finally, you will discover how to use Selenium drivers with R for more sophisticated scraping. You will create AWS instances and use R to connect a PostgreSQL database hosted on AWS. By the end of the book, you will be sufficiently confident to create end-to-end web scraping systems using R.
Table of Contents (7 chapters)

XML Path (XPath)

XPath is a syntax that provides functionality between XSL transformations and XPointer. It deals with parts of an XML document. It is used to manipulate strings, numbers, and Boolean expressions to handle the relevant parts of the XML document. XPath defines the path to a listener for each node type in an XML document. The primary syntactical structure in XPath is the expression. An expression is used to obtain an object that has one of the following four basic types:

  • Node-set
  • Boolean
  • Number
  • String

Key words in XPath are not written separately and they are written using lowercase characters. Each node in XML has a unique ID, a typed value, and a string value. Also, some nodes can even have a name. The value written to a node can be zero or atomic value strings. A sequence containing exactly one element is called a singleton. An item is identical to a singular...