按小数点(英文句号)"."(dot)分割字符串

点号作为分隔符推荐转义处理 "\."

string="head.body.tail"
> stringr::str_split(string = string,pattern = "\\.",simplify = T)[,1]
[1] "head"
> stringr::str_split(string = string,pattern = "\\.",simplify = T)[,2]
[1] "body"
> stringr::str_split(string = string,pattern = "\\.",simplify = T)[,3]
[1] "tail"

也可以使用字符类"[.]"

> stringr::str_split(string = string,pattern = "[.]",simplify = T)
     [,1]   [,2]   [,3]  
[1,] "head" "body" "tail"