1.WHY R？
#1.FOR a software environment with a primarily statistical focus.
#2.there will be an amazing visual work.
#May be a complete set of operational procedures.
2.About basics.
we need threw ourselves into the preparation with some basic knowledge of HTML, XML and the logic of regular expressions and Xpath, BUT the operations are executed from WIHTIN R!
3.RECOMMENDATION
http://www.r-datacollection.com
4.A little case study.
#爬取電影票房信息
library(stringr)
library(XML)
library(maps)
#htmlParse()用來interpreting HTML
#創建一個object
movie_parsed<-htmlParse("http://58921.com/boxoffice/wangpiao/20161004",
encoding = "UTF-8")
#the next step:extract tables/data
#readHTMLTable() for identifying and reading out those tables
tables<-readHTMLTable(movie_parsed,stringsAsFactors=FALSE)
is.matrix(tables)
is.character(tables)
is.data.frame(tables)
is.list(tables)
#so we got an "list" format#
因為R對於中文的支持不是很好，所以碰到一些中文亂碼是正常的，所以我們需要more advanced text manipulation tools.（本例中出現了部分列信息的完全丟失是因為該網站的某些列的數據是以.png格式放置的。）
5.ABC's of...
For browsing the Web, there is a hidden standard behind the scenes that structures how information is displayed.
#HTML or the hypertext markup language
Not a dedicated data storage format, but usually contains the useful information. And in general HTML is used to shape the display of information.
#XML the extensible markup language or XML
The main purpose of XML is to storage data. Thus HTML documents are interpreted and transformed in to pretty-looking output by browsers, whereas XML is "just" data wrapped in user-defined tags. The user-defined tags make XML much more flexible for storing data than HTML. Both HTML and XML-style document offer natrual, often hierarchical, structures for data storage.
(unfinished......)
#JSON or JavaScript Object Notation
基於JavaScript語言的輕量級的數據交換格式
#AJAX or "Asynchronous JavaScript and XML"
____________________________________________________________________________________________
| HTTP | R |
| XML/HTML | XPath |
| JSON | JSON parsers |
| AJAX | Selenuim |
| Plain text | Regular expressions |