r - 在R中导入Wikipedia表

Question

我定期从Wikipedia中提取表格。 Excel的Web导入不适用于Wikipedia，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)

然后该功能将从该页面下载第3张表格，该表格列出了密歇根州UP的所有县。

R中有类似的东西吗？或可以通过用户定义的函数创建？

Answer 1

软件包readHTMLTable中的功能XML是理想的选择。

尝试以下方法：

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返回HTML页面的每个元素的 data.frame列表。您可以使用 names获取有关每个元素的信息：

> 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"