Hi, I have a string vector, say, x <- "a", "aab" and anther string vector, say, y <- "a", "aa", "aab", "aabc". Is there any R function to get the indices of y for the elements of x, that is, foo(x, y) will give me the index vector c(1, 3)? I know i can combine apply() and grep("^aab$", y) to do it. But is there any elegant R function I can use? Thanks, -Luke [[alternative HTML version deleted]]