R-Partial string matches

Question

I have

x <- c("DOL3", "AnnA", "CAT5", "Johna", "543QLARA", "Poro")
y <- c("3QLAR", "DOL5", "CAT5", "ANNA", "John", "Sam")

and I want a function so that provides matches as follows:

my_function(x, y)

[1] 1, 2, 3, 4, 5, NA

Details: I need to find partial string-matches that either start the same, or end the same, or have some same letters in the middle(for example, a default value of 3 consecutive matching letter). I also need the function to give a match despite using capital letters or not. Lastly, I need the function to search for a match for each element from x to amongst all the elements of y, not a 1 to 1 comparison of the elements.

If anyone is familiar with a way to approach this please help. Thank you.

Answer 1

I think I fount the answer.

my_function_2 <- function(x, y) {
    for (i in 1:length(x)) {
     print(which(grepl(substring(x[i],1 ,3 ), y, ignore.case = TRUE)))
    }
}

It's not elegant (x must include the smaller terms (ie "3QLAR" and not "543QLARA")) and it doesn't cover everything BUT it will have to do.