xpath – 在R中抓住Youtube的评论

我正在从一系列网站(如reddit.com)中提取用户评论,Youtube也是我的另一个多汁的信息来源.我现有的刮刀是写在R：

# x is the url
html = getURL(x)
doc  = htmlParse(html,asText=TRUE) 
txt  = xpathSApply(doc,//body//text()[not(ancestor::script)][not(ancestor::style)][not(ancestor::noscript)]",xmlValue)

这在YouTube数据上不起作用,实际上,如果你看看像this这样的Youtube视频的来源,你会发现这个注释不会出现在源代码中.

有没有人有任何建议如何在这种情况下提取数据？

非常感谢！

解决方法

以下答案： R: rvest: scraping a dynamic ecommerce page

您可以执行以下操作：

devtools::install_github("ropensci/RSelenium") # Install from github

library(RSelenium)
library(rvest)
pJS <- phantom(pjs_cmd = "PATH TO phantomjs.exe") # as i am using windows
Sys.sleep(5) # give the binary a moment
remDr <- remoteDriver(browserName = 'phantomjs')
remDr$open()
remDr$navigate("https://www.youtube.com/watch?v=qRC4Vk6kisY")
remDr$getTitle()[[1]] # [1] "YouTube"

# scroll down
for(i in 1:5){      
  remDr$executeScript(paste("scroll(0,",i*10000,");"))
  Sys.sleep(3)    
}

# Get page source and parse it via rvest
page_source <- remDr$getPageSource()
author <- html(page_source[[1]]) %>% html_nodes(".user-name") %>% html_text()
text <- html(page_source[[1]]) %>% html_nodes(".comment-text-content") %>% html_text()

#combine the data in a data.frame
dat <- data.frame(author = author,text = text)

Result:
> head(dat)
              author                                                                                       text
1 Kikyo bunny simpie Omg I love fluffy puff she's so adorable when she was dancing on a rainbow it's so cute!!!
2   Tatjana Celinska                                                                                     Ciao 0
3      Yvette Austin                                                                   GET OUT OF MYÂ  HEAD!!!!
4           Susan II                                                                             Watch narhwals
5        Greg Ginger               who in the entire fandom never watched this,should be ashamed,\n\nPFFFTT!!!
6        Arnav Sinha                                                                 LOL what the hell is this?

评论1：您需要github版本,请参阅rselenium | get youtube page source

评论2：
这段代码给你最初的44条评论.一些评论有一个“显示所有答案”链接,必须点击.还要查看更多的评论,您必须点击页面底部的显示更多按钮.
在这个卓越的RSelenium教程中介绍了点击：
http://cran.r-project.org/web/packages/RSelenium/vignettes/RSelenium-basics.html