在 R 中使用类搜索和替换字符

Question

我正在尝试替换 R 中的文本。 我只想查找字母和数字之间的空格并将其删除，但是当我使用 [:alpha:] 和 [:alnum:] 进行搜索时，它会替换为该 class 运算符。

> string <- "WORD = 500 * WORD + ((WORD & 400) - (WORD & 300))"

> str_replace_all(string,
+                 "[:alpha:] & [:alnum:]",
+                 "[:alpha:]&[:alnum:]")

[1] "WORD = 500 * WORD + ((WOR[:alpha:]&[:alnum:]00) - (WOR[:alpha:]&[:alnum:]00))"

我怎样才能使用 function 让它返回 -

[1] "WORD = 500 * WORD + ((WORD&400) - (WORD&300))"

Answer 1

str_replace_all(string, "([:alpha:]) & ([:alnum:])", "\\1&\\2")

Answer 2

使用带有环视功能的sub很容易处理您的要求：

string <- "WORD = 500 * WORD + ((WORD & 400) - (WORD & 300))"
output <- gsub("(?<=\\w) & (?=\\w)", "&", string, perl=TRUE)
output

[1] "WORD = 500 * WORD + ((WORD&400) - (WORD&300))"

以下是正则表达式的简要说明：

(?<=\\w)   assert that what precedes is a word character
[ ]&[ ]    then match a space, followed by `&`, followed by another space
(?=\\w)    assert that what follows is also a word character

然后，我们只替换一个& ，两边都没有空格。

Answer 3

这是一个选项，我们匹配正则表达式查找以匹配一个或多个空格（ \\s+ ）在&之前或之后并替换为空白（ "" ）

gsub("(?<=&)\\s+|\\s+(?=&)", "", string, perl = TRUE)
#[1] "WORD = 500 * WORD + ((WORD&400) - (WORD&300))"