在R中导入维基百科表 [英] Importing wikipedia tables in R

问题描述

我定期从维基百科提取表格。 Excel的Web导入对于维基百科不能正常工作，因为它将整个页面视为表格。在Google电子表格中，我可以输入以下内容：

  = ImportHtml（http://en.wikipedia.org/wiki/Upper_Peninsula_of_Michigan ，table，3）
  

此功能将下载第3个表，其中列出所有密歇根州的UP县，从该页。

R中有什么类似的东西吗？或者可以通过用户定义的函数创建？

解决方案

函数 readHTMLTable

尝试以下操作：

 库（XML）
 doc<  -  readHTMLTable（
 doc =http://en.wikipedia.org/wiki/Upper_Peninsula_of_Michigan ）
 
 doc [[6]] 
 
 V1 V2 V3 V4 
 1县人口面积（平方英里）人口密度（每平方英里）
 2阿尔及尔9,862 918 10.7 
 3巴拉加8,735 904 9.7 
 4奇皮瓦38,413 1561 24.7 
 5三角洲38,520 1170 32.9 
 6迪金森27,427 766 35.8 
 7 Gogebic 17， 370 1102 15.8 
 8霍顿36,016 1012 35.6 
 9铁13,138 1166 11.3 
 10 Keweenaw 2,301 541 4.3 
 11 Luce 7,024 903 7.8 
 12麦金纳11,943 1022 11.7 
 13 Marquette 64,634 1821 35.5 
 14 Menominee 25,109 1043 24.3 
 15 Ontonagon 7,818 1312 6.0 
 16教科书8,903 1178 7.6 
 17总计317,258 16,420 19.3 
  

---

readHTMLTable 返回列表的 data.frame s HTML页面的ach元素。您可以使用名称获取有关每个元素的信息：

 >名称（doc）
 [1]NULL
 [2]toc
 [3]2008年上半岛县级总统选举的选举结果
 [4]空
 [5]上半岛城乡村
 [6]上半岛土地面积和县人口密度
 [7]19世纪人口普查人口普查年份上半岛县
 [8]第20和21世纪人口普查人口按县人口上半岛年份
 [9]NULL
 [ 10]NULL
 [11]NULL 
 [12]NULL
 [13]NULL
 [14]NULL
 [15]NULL
 [16]NULL 
  

I regularly extract tables from Wikipedia. Excel's web import does not work properly for wikipedia, as it treats the whole page as a table. In google spreadsheet, I can enter this:

=ImportHtml("http://en.wikipedia.org/wiki/Upper_Peninsula_of_Michigan","table",3)

and this function will download the 3rd table, which lists all the counties of the UP of Michigan, from that page.

Is there something similar in R? or can be created via a user defined function?

解决方案

The function readHTMLTable in package XML is ideal for this.

Try the following:

library(XML)
doc <- readHTMLTable(
         doc="http://en.wikipedia.org/wiki/Upper_Peninsula_of_Michigan")

doc[[6]]

            V1         V2                 V3                              V4
1       County Population Land Area (sq mi) Population Density (per sq mi)
2        Alger      9,862                918                            10.7
3       Baraga      8,735                904                             9.7
4     Chippewa     38,413               1561                            24.7
5        Delta     38,520               1170                            32.9
6    Dickinson     27,427                766                            35.8
7      Gogebic     17,370               1102                            15.8
8     Houghton     36,016               1012                            35.6
9         Iron     13,138               1166                            11.3
10    Keweenaw      2,301                541                             4.3
11        Luce      7,024                903                             7.8
12    Mackinac     11,943               1022                            11.7
13   Marquette     64,634               1821                            35.5
14   Menominee     25,109               1043                            24.3
15   Ontonagon      7,818               1312                             6.0
16 Schoolcraft      8,903               1178                             7.6
17       TOTAL    317,258             16,420                            19.3

---

readHTMLTable returns a list of data.frames for each element of the HTML page. You can use names to get information about each element:

> names(doc)
 [1] "NULL"                                                                               
 [2] "toc"                                                                                
 [3] "Election results of the 2008 Presidential Election by County in the Upper Peninsula"
 [4] "NULL"                                                                               
 [5] "Cities and Villages of the Upper Peninsula"                                         
 [6] "Upper Peninsula Land Area and Population Density by County"                         
 [7] "19th Century Population by Census Year of the Upper Peninsula by County"            
 [8] "20th & 21st Centuries Population by Census Year of the Upper Peninsula by County"   
 [9] "NULL"                                                                               
[10] "NULL"                                                                               
[11] "NULL"                                                                               
[12] "NULL"                                                                               
[13] "NULL"                                                                               
[14] "NULL"                                                                               
[15] "NULL"                                                                               
[16] "NULL" 

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