r - 尝试使用 rvest 循环命令以从多个页面抓取表

Question

我正在尝试从不同的足球队中抓取 HTML 表格。这是我想要抓取的表格，但是我想从所有球队中抓取同一个表格，以最终创建一个包含球员姓名及其数据的 CSV 文件。

http://www.pro-football-reference.com/teams/tam/2016_draft.htm

# teams
teams <- c("ATL", "TAM", "NOR", "CAR", "GNB", "DET", "MIN", "CHI", "SEA", "CRD", "RAM", "NWE", "MIA", "BUF", "NYJ", "KAN", "RAI", "DEN", "SDG", "PIT", "RAV", "SFO", "CIN", "CLE", "HTX", "OTI", "CLT", "JAX", "DAL", "NYG", "WAS", "PHI")

# loop
for(i in teams) {
  url <-paste0("http://www.pro-football-reference.com/teams/", i,"/2016-snap-counts.htm#snap_counts::none", sep="")
  webpage <- read_html(url)

  # grab table
  sb_table <- html_nodes(webpage, 'table')
html_table(sb_table)
head(sb_table)
  # bind to dataframe
df <- rbind(df, sb_table)
}

我收到一个错误，认为我应该使用 CSS 或 Xpath，而不是两者都使用，但我无法弄清楚问题到底出在哪里(我怀疑 html_nodes 命令)。谁能帮我解决这个问题吗？

Answer 1

我认为您的网址构建得很糟糕，此外，团队的名称区分大小写。你能尝试这样的事情吗？

library(rvest)
library(magrittr)

# teams
teams <- c("ATL", "TAM", "NOR", "CAR", "GNB", "DET", "MIN", "CHI", "SEA", "CRD", "RAM", "NWE", "MIA", "BUF", "NYJ", "KAN", "RAI", "DEN", "SDG", "PIT", "RAV", "SFO", "CIN", "CLE", "HTX", "OTI", "CLT", "JAX", "DAL", "NYG", "WAS", "PHI")

tables <- list()
index <- 1
for(i in teams){
  try({
  url <- paste0("http://www.pro-football-reference.com/teams/", tolower(i), "/2016_draft.htm")
  table <- url %>% 
    read_html() %>% 
    html_table(fill = TRUE)

  tables[index] <- table

  index <- index + 1

  })
}

df <- do.call("rbind", tables)

PS:我不明白为什么这个问题被否决。看起来制定得很好......