从R中的字符串中提取最后n个字符 [英] Extracting the last n characters from a string in R

问题描述

如何从 R 中的字符串中获取最后 n 个字符?有没有类似 SQL 的 RIGHT 的函数?

How can I get the last n characters from a string in R? Is there a function like SQL's RIGHT?

推荐答案

我不知道 base R 中的任何内容，但使用 substr 和nchar:

I'm not aware of anything in base R, but it's straight-forward to make a function to do this using substr and nchar:

x <- "some text in a string"

substrRight <- function(x, n){
  substr(x, nchar(x)-n+1, nchar(x))
}

substrRight(x, 6)
[1] "string"

substrRight(x, 8)
[1] "a string"

<小时>

正如@mdsumner 指出的那样，这是矢量化的.考虑:

---

This is vectorised, as @mdsumner points out. Consider:

x <- c("some text in a string", "I really need to learn how to count")
substrRight(x, 6)
[1] "string" " count"

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