只删除单词而不是数字的标点符号

Question

我正在使用 R 中的 tm 包来删除标点符号。

TextDoc <- tm_map(TextDoc, removePunctuation)

有没有一种方法可以只删除与字母/单词而不是数字有关的标点符号？

例如

我想要performance. --> performance 但我想要3.14 --> 3.14

我希望函数如何工作的示例：

wall, --> wall
expression. --> expression
ef. --> ef
A. --> A
name: --> name
:ok --> ok

91.8.10 --> 91.8.10

编辑：

TextDoc 的形式为：

Answer 1

您也可以试试这个gsub('(?<!\\d)[[:punct:]](?=\\D)?', '', text, perl = T)，其中 text 是您的文本向量。正则表达式的解释

• (?<!\\d) 任何数字字符的负向回溯
• [[:punct:]] 搜索标点符号
• (?=\\D) 后跟任何非数字字符的正向前瞻
• ? 0 或一次
• check this 用于正则表达式演示

text <- c("wall, 88.1", "expression.", "ef.", ":ok", "A.", "3.14", "91.8.10")

gsub('(?<!\\d)[[:punct:]](?=\\D)?', '', text, perl = T)
#> [1] "wall 88.1"  "expression" "ef"         "ok"         "A"         
#> [6] "3.14"       "91.8.10"


long_text <- "wall, 88.1 expression. ef. :ok A. 3.14 91.8.10"

gsub('(?<!\\d)[[:punct:]](?=\\D)?', '', long_text, perl = T)
#> [1] "wall 88.1 expression ef ok A 3.14 91.8.10"

^{由reprex package (v2.0.0) 于 2021-06-13 创建}

Answer 2

我已根据您的规范和Anil's answer below 彻底修改了我的答案，这比我原来的适用范围更广。

library(tm)

# Here we pretend that your texts are like this
text <- c("wall,", "expression.", "ef.", ":ok", "A.", "3.14", "91.8.10",
          "w.a.ll, 6513.645+1646-5")

# and we create a corpus with them, like the one you show
corp <- Corpus(VectorSource(text))

# you create a function with any of the solutions that we've provided here
# I'm taking AnilGoyal's because it's better than my rushed purrr one.

my_remove_punct <- function(x) {
  
  gsub('(?<!\\d)[[:punct:]](?=\\D)?', '', x, perl = T)

}

# pass the function to tm_map
new_corp <- tm_map(corp, my_remove_punct)

# Applying the function will give you a warning about dropping documents; but it's a bug of the TM package.


# We use this to confirm that the contents are indeed correct. The last line is a print-out of all the individual documents together.
sapply(new_corp, print)
#> [1] "wall"
#> [1] "expression"
#> [1] "ef"
#> [1] "ok"
#> [1] "A"
#> [1] "3.14"
#> [1] "91.8.10"
#> [1] "wall 6513.645+1646-5"
#> [1] "wall"                 "expression"           "ef"                  
#> [4] "ok"                   "A"                    "3.14"                
#> [7] "91.8.10"              "wall 6513.645+1646-5"

您收到的有关“丢弃文档”的警告并不真实，您可以通过打印看到。解释在this other SO question。

请注意，将来您可以通过向您的对象提供带有函数dput 的原始数据来快速获得更好的答案。像dput(TextDoc) 这样的东西。如果太多，您可以对其进行子集化。

Answer 3

试图让它不那么难看，但这是我最好的选择：

library(data.table)

TextDoc <- data.table(text = c("wall",
                      "expression.", 
                      "ef.",
                      "91.8.10",
                      "A.", 
                      "name:", 
                      ":ok"))

TextDoc[grepl("[a-zA-Z]", text), 
      text := unlist(tm_map(Corpus(VectorSource(as.vector(text))), removePunctuation))[1:length(grepl("[a-zA-Z]", text))]]   

这给了我们：

> TextDoc
         text
1:       wall
2: expression
3:         ef
4:    91.8.10
5:          A
6:       name
7:         ok