R Language Set operations Set membership for vectors


Example

The %in% operator compares a vector with a set.

v = "A"
w = c("A", "A")

w %in% v
# TRUE TRUE

v %in% w
# TRUE

Each element on the left is treated individually and tested for membership in the set associated with the vector on the right (consisting of all its distinct elements).

Unlike equality tests, %in% always returns TRUE or FALSE:

c(1, NA) %in% c(1, 2, 3, 4)
# TRUE FALSE

The documentation is at ?`%in%`.