I'm new to R and am having some trouble to create a good web scraper with R.... It has been only 5 days since I started to study this language. So, any help I'll appreciate!
Idea
I'm trying to web scraping the classification table of "Campeonato Brasileiro" from 2003 to 2021 on Wikipedia to group the teams later to analyze some stuff.
Explanation and problem
I'm scraping the page of the 2002 championship. I read the HTML page to extract the HTML nodes that I select with the "SelectorGadget" extension at Google Chrome. There is some considerations:
- The page that I'm trying to access is from the 2002 championship. I done that because it was easier to extract the links of the tables that are present on a board in the final of the page, selecting just one selector for all (tr:nth-child(9) div a) to access their links by HTML attribute "href";
- The selected CSS was from 2003 championship page.
So, in my twisted mind I thought: "Hey! I'm going to create a function to extract the tables from those pages and I'll save them in a data frame!". However, it went wrong and I'm not understanding why... When I tried to ran the "tabelageral" line, the following error returned : "Error in UseMethod("xml_find_all") : no applicable method for 'xml_find_all' applied to an object of class "character"". I think that it is reading a string instead of a xml. What am I misunderstanding here? Where is my error? The "sapply" method? Since now, thanks!
The code
library("dplyr")
library("rvest")
link_wikipedia <- "https://pt.wikipedia.org/wiki/Campeonato_Brasileiro_de_Futebol_de_2002"
pagina_wikipedia <- read_html(link_wikipedia)
links_temporadas <- pagina_wikipedia %>%
html_nodes("tr:nth-child(9) div a") %>%
html_attr("href") %>%
paste("https://pt.wikipedia.org", ., sep = "")
tabela <- function(link){
pagina_tabela <- read_html(link)
tabela_wiki = link %>%
html_nodes("table.wikitable") %>%
html_table() %>%
paste(collapse = "|")
}
tabela_geral <- sapply(links_temporadas, FUN = tabela, USE.NAMES = FALSE)
tabela_final <- data.frame(tabela_geral)