In Zyufei/Rstudy: Easily Harvest (Scrape) Web Pages

knitr::opts_chunk$set(
  collapse = TRUE, 
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  fig.path = "README-"  
)

rvest

rvest helps you scrape information from web pages. It is designed to work with magrittr to make it easy to express common web scraping tasks, inspired by libraries like beautiful soup.

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

rating <- lego_movie %>% 
  html_nodes("strong span") %>%
  html_text() %>%
  as.numeric()
rating

cast <- lego_movie %>%
  html_nodes("#titleCast .itemprop span") %>%
  html_text()
cast

poster <- lego_movie %>%
  html_nodes(".poster img") %>%
  html_attr("src")
poster

Overview

The most important functions in rvest are:

• Create an html document from a url, a file on disk or a string containing html with read_html().

• Select parts of a document using css selectors: html_nodes(doc, "table td") (or if you've a glutton for punishment, use xpath selectors with html_nodes(doc, xpath = "//table//td")). If you haven't heard of selectorgadget, make sure to read vignette("selectorgadget") to learn about it.

• Extract components with html_tag() (the name of the tag), html_text() (all text inside the tag), html_attr() (contents of a single attribute) and html_attrs() (all attributes).

• (You can also use rvest with XML files: parse with xml(), then extract components using xml_node(), xml_attr(), xml_attrs(), xml_text() and xml_tag().)

• Parse tables into data frames with html_table().

• Extract, modify and submit forms with html_form(), set_values() and submit_form().

• Detect and repair 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(), forward(), submit_form() and so on. (This is still a work in progress, so I'd love your feedback.)

To see examples of these function in use, check out the demos.

Installation

Install the release version from CRAN:

install.packages("rvest")

Or the development version from github

# install.packages("devtools")
devtools::install_github("hadley/rvest")

Inspirations

• Python: Robobrowser, beautiful soup.

Zyufei/Rstudy documentation built on May 19, 2019, 4:04 p.m.