用 R 删除某个单词之前的字符串

Question

我有一个需要清理的字符向量。具体来说，我想删除“投票”一词之前的数字。请注意，数字用逗号分隔千位，因此更容易将其视为字符串。

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

感谢您提供的任何帮助！

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

你可以使用

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"

请参阅online R demo 和online regex demo。

详情

• (\\s){2,} - 匹配 2 个或更多空白字符，同时捕获将在替换模式中使用 \1 占位符重新插入的最后一次出现
• | - 或
• \\d - 一个数字
• [0-9,]* - 0 个或多个数字或逗号
• \\s* - 0+ 个空白字符
• (Votes) - 第 2 组（将使用 \2 占位符在输出中恢复）：Votes 子字符串。

请注意，trimws 将删除所有前导/尾随空格。

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"

要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"

以下版本会去掉“投票”一词之前的所有数字，即使其中包含逗号或句点：

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

如果你也想要这个标签，那就扔掉gsub 部分：

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

如果你想提取所有的数字：

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