Rvest R not getting inner table - html

Question

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

Answer 1

The first table with the names has a complicated structure and seems to be very difficult to convert into a standard format. At least I didn't succeed.
A summary of the number of medals by sport and the total medals can be obtained with
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
Then there is another table summarizing all competitors that you can get with
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
And this is the table of multiple medalists:
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.