我的数据集中的变量之一包含 Google 搜索结果页面的 URL。我想从这些 URL 中提取搜索关键字。
示例数据集:
keyw <- structure(list(user = structure(c(1L, 1L, 1L, 2L, 2L, 2L), .Label = c("p1", "p2"), class = "factor"),
url = structure(c(3L, 5L, 4L, 1L, 2L, 6L), .Label = c("https://www.google.nl/search?q=five+fingers&ie=utf-8&oe=utf-8&gws_rd=cr,ssl&ei=kERoVbmMO6fp7AaGioCYAw", "https://www.google.nl/search?q=five+fingers&ie=utf-8&oe=utf-8&gws_rd=cr,ssl&ei=kERoVbmMO6fp7AaGioCYAw#safe=off&q=five+short+fingers+", "https://www.google.nl/search?q=high+five&ie=utf-8&oe=utf-8&gws_rd=cr,ssl&ei=bENoVZSqL4ON7Qb5wIDIDg", "https://www.google.nl/search?q=high+five&ie=utf-8&oe=utf-8&gws_rd=cr,ssl&ei=bENoVZSqL4ON7Qb5wIDIDg#safe=off&q=high+five+with+a+chair", "https://www.google.nl/search?q=high+five&ie=utf-8&oe=utf-8&gws_rd=cr,ssl&ei=bENoVZSqL4ON7Qb5wIDIDg#safe=off&q=high+five+with+handshake", "https://www.youtube.com/watch?v=6HOallAdtDI"), class = "factor")),
.Names = c("user", "url"), class = "data.frame", row.names = c(NA, -6L))
到目前为止,我能够从 URL 中提取搜索关键字部分:
keyw$words <- sapply(str_extract_all(keyw$url, 'q=([^&#]*)'),paste, collapse=",")
但是,这仍然没有给我想要的结果。上面的代码给出了以下结果:
> keyw$words
[1] "q=high+five"
[2] "q=high+five,q=high+five+with+handshake"
[3] "q=high+five,q=high+five+with+a+chair"
[4] "q=five+fingers"
[5] "q=five+fingers,q=five+short+fingers+"
[6] ""
此输出存在三个问题:
q=high+five
, 我需要 high,five
. NA
. 想要的结果应该是:
> keyw$words
[1] "high,five"
[2] "high,five,with,handshake"
[3] "high,five,with,a,chair"
[4] "five,fingers"
[5] "five,short,fingers"
[6] NA
我该如何解决这个问题?
最佳答案
评论后的另一个更新(看起来太复杂了,但这是我目前能做到的最好的 :)):
keyw$words <- sapply(str_extract_all(str_extract(keyw$url,"https?:[/]{2}[^/]*google.*[/].*"),'(?<=q=|[+])([^$+#&]+)(?!.*q=)'),function(x) if(!length(x)) NA else paste(x,collapse=","))
> keyw$words
[1] "high,five" "high,five,with,handshake" "high,five,with,a,chair" "five,fingers"
[5] "five,short,fingers" NA
变化是输入到 str_extract_all 的过滤器,从完整向量更改为“过滤”以匹配正则表达式,任何正则表达式都可以去那里以或多或少地精确匹配您想要的。
这里的正则表达式是:
http
http s?
0 或 1 秒 [/]{2}
正好是两个斜杠(使用字符类避免需要丑陋的 \\/
结构并使事情更具可读性 [^/]*
任意数量的非斜杠字符 google.*[/]
匹配litteraly google,然后是任何东西到最后/.*
最后在最后一个斜杠后匹配或不匹配 将 * 替换为 + 以确保存在参数(
+
将要求前面的字符至少出现一次)受@BrodieG 启发的更新,如果没有匹配将返回 NA,但如果有
q=
仍将匹配任何站点在参数中。还是用同样的方法:
> keyw$words <- sapply(str_extract_all(keyw$url,'(?:(?<=q=|\\+)([^$+#&]+)(?!.*q=))'),function(x) if(!length(x)) NA else paste(x,collapse=","))
> keyw$words
[1] "high,five" "high,five,with,handshake" "high,five,with,a,chair"
[4] "five,fingers" "five,short,fingers" NA
Regex demo
(后视
(?<=)
确保在单词之前的某处有 q= 或 +,负前瞻 (?!)
确保我们在行尾之前找不到 q=。字符类不允许 + 号停在每个单词上。
关于regex - 如何从 Google 搜索结果页面 URL 中提取关键字?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30530616/