| duplicated {base} | R Documentation |
Determines which elements of a vector are duplicates of elements with smaller subscripts, and returns a logical vector indicating which elements are duplicates.
duplicated(x)
x |
an atomic vector |
x <- c(9:20, 1:5, 3:7, 0:8) ## extract unique elements (xu <- x[!duplicated(x)]) all(xu == unique(x)) # TRUE, but unique(x) is more efficient all(0:20 == sort(x[!duplicated(x)]))