Nested Loop using apply functions in R

Question

I have the following function to get some urls from a website using RSelinium and phantomjs.

get_url <- function(url){
  rdr$navigate(url)
  li <- rdr$findElements(using = 'xpath',  "//div[@data-id]")
  str <- sapply(li, function(x){x$getElementAttribute('outerHTML')})
  if(length(str)>1){
  tree <- htmlParse(str)
  url <- getNodeSet(tree, '//div//a[@class="link url"]')
  url <- sapply(url, xmlGetAttr, 'href')
  }
}

And the url is stored in a 30 x 60 matrix.

I tried doing this using the following nested loop.

for(i in 1:ncol(offset_url)){
  for(j in 1:nrow(offset_url)){
    url_list <- rbind(url_list,get_url(offset_url[j,i]))
  }
}

However, it takes a lot of time to execute.

Is there a way that I can use apply functions to rduce the time?

Answer 1

这有帮助吗？

do.call(rbind,list(mapply(function(x,y) get_url(offset_url[x,y]),x=row(offset_url),y=col(offset_url))))