用R去掉某个单词前的字符串

Question

我有一个字符向量需要清理。具体来说，我想删除单词 "Votes." 之前的数字请注意，该数字用逗号分隔千位，因此将其视为字符串更容易。

我知道 gsub("*. Votes","", text) 会删除所有内容，但我该如何删除数字？另外，如何将重复的 space 折叠成一个 space?

感谢您的帮助！

示例数据：

text <- "STATE QUESTION NO. 1                       Amendment to Title 15 of the Nevada Revised Statutes Shall Chapter 202 of the Nevada Revised Statutes be amended to prohibit, except in certain circumstances, a person from selling or transferring a firearm to another person unless a federally-licensed dealer first conducts a federal background check on the potential buyer or transferee?                    558,586 Votes"

Answer 1

您可以使用

text <- "STATE QUESTION NO. 1                       Amendment to Title 15 of the Nevada Revised Statutes Shall Chapter 202 of the Nevada Revised Statutes be amended to prohibit, except in certain circumstances, a person from selling or transferring a firearm to another person unless a federally-licensed dealer first conducts a federal background check on the potential buyer or transferee?                    558,586 Votes"
trimws(gsub("(\s){2,}|\d[0-9,]*\s*(Votes)", "\1\2", text))
# => [1] "STATE QUESTION NO. 1 Amendment to Title 15 of the Nevada Revised Statutes Shall Chapter 202 of the Nevada Revised Statutes be amended to prohibit, except in certain circumstances, a person from selling or transferring a firearm to another person unless a federally-licensed dealer first conducts a federal background check on the potential buyer or transferee? Votes"

参见online R demo and the online regex demo。

详情

(\s){2,} - 匹配 2 个或更多空白字符，同时捕获将使用替换模式中的 </code> 占位符重新插入的最后一次出现 </li> <li><code>| - 或
\d - 一个数字
[0-9,]* - 0 个或更多数字或逗号
\s* - 0+ 个空白字符
(Votes) - 第 2 组（将使用 </code> 占位符在输出中恢复）：<code>Votes 子字符串。

请注意 trimws 将删除任何 leading/trailing 空格。

Answer 2

最简单的方法是 stringr:

> library(stringr)
> regexp <- "-?[[:digit:]]+\.*,*[[:digit:]]*\.*,*[[:digit:]]* Votes+"
> str_extract(text,regexp)
[1] "558,586 Votes"

做同样的事情但只提取数字，将其包装在 gsub:

> gsub('\s+[[:alpha:]]+', '', str_extract(text,regexp))
[1] "558,586"

这是一个版本，它会删除单词 "Votes" 之前的所有数字，即使其中有逗号或句点：

> gsub('\s+[[:alpha:]]+', '', unlist(regmatches (text,gregexpr("-?[[:digit:]]+\.*,*[[:digit:]]*\.*,*[[:digit:]]* Votes+",text) )) )
[1] "558,586"

如果你也想要标签，那么就扔掉 gsub 部分：

> unlist(regmatches (text,gregexpr("-?[[:digit:]]+\.*,*[[:digit:]]*\.*,*[[:digit:]]* Votes+",text) )) 
[1] "558,586 Votes"

如果您想提取所有数字：

> unlist(regmatches (text,gregexpr("-?[[:digit:]]+\.*,*[[:digit:]]*\.*,*[[:digit:]]*",text) ))
[1] "1"       "15"      "202"     "558,586"

用R去掉某个单词前的字符串

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