如何在 R 中读取和解析网页内容

发布于 2024-08-14 02:47:43 字数 118 浏览 10 评论 0原文

我想阅读 URL 的内容（例如 http://www.haaretz.com/ ）在 R 中。我想知道我该怎么做

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枫林﹌晚霞¤ 2024-08-21 02:47:43

不太确定你想如何处理该页面，因为它真的很乱。正如我们在这个著名的 stackoverflow 问题中重新学习的，在 html 上执行正则表达式不是一个好主意，因此您肯定会希望使用 XML 包来解析它。

下面是一个帮助您入门的示例：

require(RCurl)
require(XML)
webpage <- getURL("http://www.haaretz.com/")
webpage <- readLines(tc <- textConnection(webpage)); close(tc)
pagetree <- htmlTreeParse(webpage, error=function(...){}, useInternalNodes = TRUE)
# parse the tree by tables
x <- xpathSApply(pagetree, "//*/table", xmlValue)  
# do some clean up with regular expressions
x <- unlist(strsplit(x, "\n"))
x <- gsub("\t","",x)
x <- sub("^[[:space:]]*(.*?)[[:space:]]*$", "\\1", x, perl=TRUE)
x <- x[!(x %in% c("", "|"))]

这会产生一个主要由网页文本（以及一些 javascript）组成的字符向量：

> head(x)
[1] "Subscribe to Print Edition"              "Fri., December 04, 2009 Kislev 17, 5770" "Israel Time:Â 16:48Â (EST+7)"           
[4] "Â Â Make Haaretz your homepage"          "/*check the search form*/"               "function chkSearch()"

Not really sure how you want to process that page, because it's really messy. As we re-learned in this famous stackoverflow question, it's not a good idea to do regex on html, so you will definitely want to parse this with the XML package.

Here's an example to get you started:

require(RCurl)
require(XML)
webpage <- getURL("http://www.haaretz.com/")
webpage <- readLines(tc <- textConnection(webpage)); close(tc)
pagetree <- htmlTreeParse(webpage, error=function(...){}, useInternalNodes = TRUE)
# parse the tree by tables
x <- xpathSApply(pagetree, "//*/table", xmlValue)  
# do some clean up with regular expressions
x <- unlist(strsplit(x, "\n"))
x <- gsub("\t","",x)
x <- sub("^[[:space:]]*(.*?)[[:space:]]*$", "\\1", x, perl=TRUE)
x <- x[!(x %in% c("", "|"))]

This results in a character vector of mostly just webpage text (along with some javascript):

> head(x)
[1] "Subscribe to Print Edition"              "Fri., December 04, 2009 Kislev 17, 5770" "Israel Time:Â 16:48Â (EST+7)"           
[4] "Â Â Make Haaretz your homepage"          "/*check the search form*/"               "function chkSearch()"

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