r - R中的“救援”命令？

Question

我有这个代码：

library(rvest)
url_list <- c("https://github.com/rails/rails/pull/100", 
               "https://github.com/rails/rails/pull/200", 
               "https://github.com/rails/rails/pull/300")

mine <- function(url){
  url_content  <- html(url)
  url_mainnode <- html_node(url_content, "*")
  url_mainnode_text <- html_text(url_mainnode)
  url_mainnode_text <- gsub("\n", "", url_mainnode_text) # clean up the text
  url_mainnode_text
}

messages <- lapply(url_list, mine)

然而，当我把列表加长时，我往往会遇到

Error in html.response(r, encoding = encoding) : 
  server error: (500) Internal Server Error 

我知道在 Ruby 中，我可以使用它rescue来继续遍历列表，即使应用函数的一些尝试失败了。R中有类似的东西吗？

Answer 1

一种选择是使用try(). 有关更多信息，请参见此处。这是一个实现：

library(rvest)
url_list <- c("https://github.com/rails/rails/pull/100", 
               "https://github.com/rails/rails/pull/200", 
               "https://github.com/rails/rails/pull/300")

mine <- function(url){
  try(url_content  <- html(url))
  url_mainnode <- html_node(url_content, "*")
  url_mainnode_text <- html_text(url_mainnode)
  url_mainnode_text <- gsub("\n", "", url_mainnode_text) # clean up the text
  url_mainnode_text
}

messages <- lapply(url_list, mine)