Extract the first (or last) n characters of a string

See ?substr

R> substr(a, 1, 4)
[1] "left"

The stringr package provides the str_sub function, which is a bit easier to use than substr, especially if you want to extract right portions of your string :

R> str_sub("leftright",1,4)
[1] "left"
R> str_sub("leftright",-5,-1)
[1] "right"

You can easily obtain Right() and Left() functions starting from the Rbase package:

• right function

  right = function (string, char) {
      substr(string,nchar(string)-(char-1),nchar(string))
  }
  

• left function

  left = function (string,char) {
      substr(string,1,char)
  }
  

you can use those two custom-functions exactly as left() and right() in excel. Hope you will find it useful