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You're reading from  Learning R Programming

Product typeBook
Published inOct 2016
Reading LevelBeginner
PublisherPackt
ISBN-139781785889776
Edition1st Edition
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Author (1)
Kun Ren
Kun Ren
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Kun Ren

Kun Ren has used R for nearly 4 years in quantitative trading, along with C++ and C#, and he has worked very intensively (more than 8-10 hours every day) on useful R packages that the community does not offer yet. He contributes to packages developed by other authors and reports issues to make things work better. He is also a frequent speaker at R conferences in China and has given multiple talks. Kun also has a great social media presence. Additionally, he has substantially contributed to various projects, which is evident from his GitHub account: https://github.com/renkun-ken https://cn.linkedin.com/in/kun-ren-76027530 http://renkun.me/ http://renkun.me/formattable/ http://renkun.me/pipeR/ http://renkun.me/rlist/
Read more about Kun Ren

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Extracting data from web pages using CSS selectors


In R, the easiest-to-use package for web scraping is rvest. Run the following code to install the package from CRAN:

install.packages("rvest") 

First, we load the package and use read_html() to read data/single-table.html and try to extract the table from the web page:

library(rvest) 
## Loading required package: xml2 
single_table_page <- read_html("data/single-table.html") 
single_table_page 
## {xml_document} 
## <html> 
## [1] <head>\n  <title>Single table</title>\n</head> 
## [2] <body>\n  <p>The following is a table</p>\n  <table i ... 

Note that single_table_page is a parsed HTML document, which is a nested data structure of HTML nodes.

A typical process for scraping information from such a web page using rvest functions is: First, locate the HTML nodes from which we need to extract data. Then, use either the CSS selector or XPath expression...

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Learning R Programming
Published in: Oct 2016Publisher: PacktISBN-13: 9781785889776

Author (1)

author image
Kun Ren

Kun Ren has used R for nearly 4 years in quantitative trading, along with C++ and C#, and he has worked very intensively (more than 8-10 hours every day) on useful R packages that the community does not offer yet. He contributes to packages developed by other authors and reports issues to make things work better. He is also a frequent speaker at R conferences in China and has given multiple talks. Kun also has a great social media presence. Additionally, he has substantially contributed to various projects, which is evident from his GitHub account: https://github.com/renkun-ken https://cn.linkedin.com/in/kun-ren-76027530 http://renkun.me/ http://renkun.me/formattable/ http://renkun.me/pipeR/ http://renkun.me/rlist/
Read more about Kun Ren