R, Xpath, 抓取

Question

我想使用 Xpath 引用和 R 抓取网站。我对此很陌生，但据我所知，我编写了以下代码，

 A <- "http://www.strompreis.elcom.admin.ch/ShowCat.aspx?placeNumber=5661&OpID=2&Period=2015"
 doc <- htmlParse(A)
 A <- xpathApply(A,path="//tr[1]/td/span",fun=xmlAttrs)

但是，我得到了以下错误，

Error in UseMethod("xpathApply") : 
  no applicable method for 'xpathApply' applied to an object of class "character"

我有兴趣对以下 xpath 进行转义：//tr[1]/td/span 问题是什么？代码有什么问题？

Answer 1

使用 rvest，这似乎可行：

library(rvest)
A="http://www.strompreis.elcom.admin.ch/ShowCat.aspx?placeNumber=5661&OpID=2&Period=2015"
A %>% html() %>% html_nodes(xpath="//tr[1]/td/span") %>% html_text()

Answer 2

您在 xpathApply 部分中放置了 A 而不是 doc...

A="http://www.strompreis.elcom.admin.ch/ShowCat.aspx?placeNumber=5661&OpID=2&Period=2015"
doc <- htmlParse(A)
xpathApply(doc,path="//tr[1]/td/span",fun=xmlAttrs)

R, Xpath, 抓取

R, Xpath, Scrape

r

xpath

scrape