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I'm trying to retrieve the Medals Table inside Wikipedia for Olympics 2012.

library(rvest) 
library(magrittr)
url <- "https://en.wikipedia.org/wiki/United_States_at_the_2012_Summer_Olympics" 

    xpath0 <- '//*[@id="mw-content-text"]/table[1]'
    xpath1 <- '//*[@id="mw-content-text"]/table[2]'
    xpath2 <- '//*[@id="mw-content-text"]/table[2]/tbody/tr/td[1]'
    xpath3 <- '//*[@id="mw-content-text"]/table[2]/tbody/tr/td[1]/table'

    tb <- url %>%
      html() %>%
      html_nodes(xpath=xpath0) %>%
      html_nodes("") %>%
      html_table()

xpath0 or xpath1 return an error

Error in parse_simple_selector(stream) : 
  Expected selector, got <EOF at 1>

xpath2 and xpath3 return empty lists.

At same time I tried to use Selectorgadget (https://cran.r-project.org/web/packages/rvest/vignettes/selectorgadget.html) to point to the exact element. I got

//td[(((count(preceding-sibling::) + 1) = 1) and parent::)] | //*[contains(concat( " ", @class, " " ), concat( " ", "headerSortDown", " " ))]

and the Error

Error in parse_simple_selector(stream) : Expected selector, got

I really appreciate any help.

Joa

4

1 回答 1

1

第一个带有名称的表结构复杂，似乎很难转换为标准格式。至少我没有成功。

可以通过以下方式获得按运动的奖牌数量和总奖牌的摘要

library(rvest) #v.0.2.0.9000
url <- "https://en.wikipedia.org/wiki/United_States_at_the_2012_Summer_Olympics" 
tb <- read_html(url) %>% html_node("table.wikitable:nth-child(2)") %>% html_table(fill=TRUE)
#> head(tb)
#   Medals by sport   NA   NA   NA    NA NA NA
#1            Sport 01 ! 02 ! 03 ! Total NA NA
#2         Swimming   16    9    6    31 NA NA
#3    Track & field    9   12    7    28 NA NA
#4       Gymnastics    3    1    2     6 NA NA
#5         Shooting    3    0    1     4 NA NA
#6           Tennis    3    0    1     4 NA NA

然后是另一个表格，总结了您可以与之合作的所有竞争对手

tb2 <- read_html(url) %>% html_node("table.wikitable:nth-child(20)") %>% html_table()
#> head(tb2)
#                        Sport Men Women Total
#1                     Archery   3     3     6
#2 Athletics (track and field)  63    62   125
#3                   Badminton   2     1     3
#4                  Basketball  12    12    24
#5                      Boxing   9     3    12
#6                    Canoeing   5     2     7

这是多个奖牌获得者的表格：

tb3 <- read_html(url) %>%  html_node("table.wikitable:nth-child(8)") %>% html_table(fill=TRUE)
#> head(tb3)
#  Multiple medalists            NA   NA   NA   NA    NA NA
#1               Name         Sport 01 ! 02 ! 03 ! Total NA
#2     Michael Phelps      Swimming    4    2    0     6 NA
#3     Missy Franklin      Swimming    4    0    1     5 NA
#4    Allison Schmitt      Swimming    3    1    1     5 NA
#5        Ryan Lochte      Swimming    2    2    1     5 NA
#6      Allyson Felix Track & field    3    0    0     3 NA

It really depends on which table you want to have, as pointed out by @Metrics. There are many tables on that page.

于 2015-07-26T19:51:30.930 回答