regex - gsub() 中有超过 9 个反向引用

Question

如何使用具有 9 个以上反向引用的 gsub？
我希望下面示例中的输出为“e、g、i、j、o”。

> test <- "abcdefghijklmnop"
> gsub("(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)(\\w)", "\\5, \\7, \\9, \\10, \\15", test, perl = TRUE)
[1] "e, g, i, a0, a5"

Answer 1

见 Regular Expressions with The R Language :

You can use the backreferences \1 through \9 in the replacement text to reinsert text matched by a capturing group. There is no replacement text token for the overall match. Place the entire regex in a capturing group and then use \1.

但是使用 PCRE 你应该可以使用 named groups .所以试试 (?P< name > regex )用于分组命名和 (?P= name )作为反向引用。