删除R中除反斜杠以外的所有标点符号

Question

我正在尝试从数据集中提取 html 链接。我正在使用 strsplit 然后 grep 来查找带有链接的子字符串，但结果在字符串的开头或结尾都有不需要的字符....如何仅提取具有所需模式的字符串或保留字符串想要的图案

他就是我目前正在做的事情。

1) 我使用 strplit 和 " " (空格) 作为分隔符来分割一段文本

2）接下来我grep strsplit的结果来找到模式

例如grep("https:\/\/support.google.com\/blogger\/topic\/[0-9]",r)

3) 结果的一些变化如下所示....

https://support.google.com/blogger/topic/12457 
https://support.google.com/blogger/topic/12457.
[https://support.google.com/blogger/topic/12457]  
<<https://support.google.com/blogger/topic/12457>>
https://support.google.com/blogger/topic/12457,
https://support.google.com/blogger/topic/12457),
xxxxxxhttps://support.google.com/blogger/topic/12457),hhhththta
etc...

如何只提取“https://support.google.com/blogger/topic/12457”或提取脏数据后如何删除不需要的标点符号

提前致谢。

Answer 1

qdapRegex 包有一个很棒的函数 rm_url 非常适合这个例子。

install.packages('qdapRegex')
library(qdapRegex)

urls <- YOUR_VECTOR_OF_URLS
rm_url(urls, extract = T)

Answer 2

如果数据在某些时候是 HTML，你可以试试这个：

library(XML)
urls <- getNodeSet(htmlParse(htmldata), "//a[contains(@href, 'support.google.com')]/@href"))

Answer 3

使用rex 可能会使此类任务更简单一些。

# generate dataset
x <- c(
"https://support.google.com/blogger/topic/12457
https://support.google.com/blogger/topic/12457.
https://support.google.com/blogger/topic/12457] 
<<https://support.google.com/blogger/topic/12457>>
https://support.google.com/blogger/topic/12457,
https://support.google.com/blogger/topic/12457),
xxxxxxhttps://support.google.com/blogger/topic/12457),hhhththta")

# extract urls
# note you don't have to worry about escaping the html string yourself
library(rex)    
re <- rex(
  capture(name = "url",
    "https://support.google.com/blogger/topic/",
    digits
    ))

re_matches(x, re, global = TRUE)[[1]]
#>                                             url
#>1 https://support.google.com/blogger/topic/12457
#>2 https://support.google.com/blogger/topic/12457
#>3 https://support.google.com/blogger/topic/12457
#>4 https://support.google.com/blogger/topic/12457
#>5 https://support.google.com/blogger/topic/12457
#>6 https://support.google.com/blogger/topic/12457
#>7 https://support.google.com/blogger/topic/12457