season <- c(Summer = 0L, Fall = 1L,
Winter = 2L, Spring = 3L)
# The member whose value is 2
winter <- names(which(season == 2))
# winter = Winter
cat("winter =", winter, "\n")
# An unknown value finds nothing, no error
unknown <- names(which(season == 9))
cat("length(unknown) =", length(unknown), "\n")
# length(unknown) = 0