Test if a vector contains a given element

Question

How to check if a vector contains a given value?

Answer 1

I really like grep() and grepl() for this purpose.

grep() returns a vector of integers, which indicate where matches are.

yo <- c("a", "a", "b", "b", "c", "c")

grep("b", yo)
[1] 3 4

grepl() returns a logical vector, with "TRUE" at the location of matches.

yo <- c("a", "a", "b", "b", "c", "c")

grepl("b", yo)
[1] FALSE FALSE  TRUE  TRUE FALSE FALSE

These functions are case-sensitive.