Select a substring of characters from the end of a character string in R

I have a vector of character strings

vec <- c("1ZQOYNBAA55", "2JSNHGKLRBB66", "3HVXCC77", "4LDD88", "5CIFMTLYXEE99")

> vec
[1] "1ZQOYNBAA55"   "2JSNHGKLRBB66" "3HVXCC77"      "4LDD88"        "5CIFMTLYXEE99"

…and I would like to get the last 3 characters from each string. To get the first 3 characters, I can use substr()

substr(vec,1,3)

I would have thought something like substr() with a "fromLast" argument might exist

vec_ends <- substr(vec,1,3, fromLast = TRUE)

With an expected output

> vec_ends
[1] "A55" "B66" "C77" "D88" "E99"

But substr() only works one way. In my dataset the string lengths are variable so no reference to absolute character numbers or string lengths can be made, and there are no consistent separators of delimiting characters for a string split. Does anyone know of an easy way to do this in R?

>Solution :

You could use a sub() approach:

vec_ends <- sub(".*(.{3})$", "\\1", vec)
vec_ends

[1] "A55" "B66" "C77" "D88" "E99"