无法浏览新闻网站

Question

我正在从以下新闻提要rss http://indianexpress.com/section/india/feed/创建一个数据集

我正在从这个xml读取以下数据

• 标题
• 标题url
• 酒吧约会

我现在使用标题url来获取描述(概要，在主标题下面)-通过点击每个url并抓取数据。

然而，我正面临向量长度(197)与其他描述( 200)不匹配的问题。正因为如此，我无法创建我的数据文件。

有人能帮忙吗?我怎样才能有效地抓取数据？

下面的代码是可复制的

library("httr")
library("RCurl")
library("jsonlite")
library("lubridate")
library("rvest")
library("XML")
library("stringr")

url = "http://indianexpress.com/section/india/feed/"

newstopics = getURL(url)

newsxml = xmlParse(newstopics)

title <- xpathApply(newsxml, "//item/title", xmlValue)
title <- unlist(title)

titleurl <- xpathSApply(newsxml, '//item/link', xmlValue)
pubdate <- xpathSApply(newsxml, '//item/pubDate', xmlValue)

t1 = Sys.time()
desc <- NULL

for (i in 1:length(titleurl)){

  page = read_html(titleurl[i])
  temp = html_text(html_nodes(page,'.synopsis'))
  desc = c(desc,temp)

}

print(difftime(Sys.time(), t1, units = 'sec'))

desc = gsub("\n",' ',desc)

newsdata = data.frame(title,titleurl,desc,pubdate)

我得到以下错误：

Error in data.frame(title, titleurl, desc, pubdate) : 
arguments imply differing number of rows: 200, 197

Answer 1

您可以执行以下操作：

library(tidyverse)
library(xml2)
library(rvest)

feed <- read_xml("http://indianexpress.com/section/india/feed/")

# helper function to extract information from the item node
item2vec <- function(item){
  tibble(title = xml_text(xml_find_first(item, "./title")),
         link = xml_text(xml_find_first(item, "./link")),
         pubDate = xml_text(xml_find_first(item, "./pubDate")))
}

dat <- feed %>% 
  xml_find_all("//item") %>% 
  map_df(item2vec)

# The following takes a while
dat <- dat %>% 
  mutate(desc = map_chr(dat$link, ~read_html(.) %>% html_node('.synopsis') %>% html_text))

它为您提供了一个包含4列的data.frame/tibble：

> glimpse(dat)
Observations: 200
Variables: 4
$ title   <chr> "Common man has no problem with note ban, says Santosh Gangwar", "Bombay High Court comes...
$ link    <chr> "http://indianexpress.com/article/india/india-news-india/demonetisation-note-ban-cash-cru...
$ pubDate <chr> "Mon, 21 Nov 2016 20:04:21 +0000", "Mon, 21 Nov 2016 20:01:43 +0000", "Mon, 21 Nov 2016 1...
$ desc    <chr> "MoS for Finance speaks to Indian Express in Bareilly, his Lok Sabha constituency.", "The...

P.S.：要获取每个item的所有信息，您可以使用：

dat <- feed %>% 
  xml_find_all("//item") %>% 
  map_df(~xml_children(.) %>% {set_names(xml_text(.), xml_name(.))} %>% t %>% as_tibble)