R网页抓取多个页面

时间:2016-04-17 23:52:49

标签: html r web-scraping rvest

我正在制作网络抓取计划,以搜索特定的葡萄酒,并返回该品种的当地葡萄酒清单。我遇到的问题是多页结果。下面的代码是我正在使用的基本示例

url2 <- "http://www.winemag.com/?s=washington+merlot&search_type=reviews"
htmlpage2 <- read_html(url2)
names2 <- html_nodes(htmlpage2, ".review-listing .title")
Wines2 <- html_text(names2)

对于此特定搜索,共有39页结果。我知道网址更改为http://www.winemag.com/?s=washington%20merlot&drink_type=wine&page=2,但是有一种简单的方法可以让代码循环遍历所有返回的页面,并将所有39个页面的结果编译成单个列表吗?我知道我可以手动完成所有网址,但这看起来有点矫枉过正。

2 个答案:

答案 0 :(得分:13)

如果您希望将所有信息都设为purrr::map_df(),则可以使用data.frame执行类似操作:

library(rvest)
library(purrr)

url_base <- "http://www.winemag.com/?s=washington merlot&drink_type=wine&page=%d"

map_df(1:39, function(i) {

  # simple but effective progress indicator
  cat(".")

  pg <- read_html(sprintf(url_base, i))

  data.frame(wine=html_text(html_nodes(pg, ".review-listing .title")),
             excerpt=html_text(html_nodes(pg, "div.excerpt")),
             rating=gsub(" Points", "", html_text(html_nodes(pg, "span.rating"))),
             appellation=html_text(html_nodes(pg, "span.appellation")),
             price=gsub("\\$", "", html_text(html_nodes(pg, "span.price"))),
             stringsAsFactors=FALSE)

}) -> wines

dplyr::glimpse(wines)
## Observations: 1,170
## Variables: 5
## $ wine        (chr) "Charles Smith 2012 Royal City Syrah (Columbia Valley (WA)...
## $ excerpt     (chr) "Green olive, green stem and fresh herb aromas are at the ...
## $ rating      (chr) "96", "95", "94", "93", "93", "93", "93", "93", "93", "93"...
## $ appellation (chr) "Columbia Valley", "Columbia Valley", "Columbia Valley", "...
## $ price       (chr) "140", "70", "70", "20", "70", "40", "135", "50", "60", "3...

答案 1 :(得分:6)

您可以在网址的矢量lapply上进行操作,您可以将基本网址粘贴到序列中:

library(rvest)

wines <- lapply(paste0('http://www.winemag.com/?s=washington%20merlot&drink_type=wine&page=', 1:39),
                function(url){
                    url %>% read_html() %>% 
                        html_nodes(".review-listing .title") %>% 
                        html_text()
                })

结果将在包含每个页面元素的列表中返回。