Regex R lookbehind

Question

如何在n中的此字符串中的colon之前找到R个字词？我使用stringr但是会​​优先使用正则表达式。

Input on income economic activities: Small business, self-emp…

谢谢， 即

Answer 1

Base R解决方案：

n <- 4
pattern <- paste0("(\\w+ ?){", n, "}(?=:)")
regmatches(s, regexpr(pattern, s, perl = T))

[1] "on income economic activities"

Answer 2

执行：

New Size(10,20,30)

替换str_extract(str, "(\\w+ ?){3}:") [1] "income economic activities:"

的3