Distinct values in order of first appearance (one NaN at most). Equivalent to R's unique().
unique()
unique([3, 1, 3, 2, 1]); // [3, 1, 2] Copy
unique([3, 1, 3, 2, 1]); // [3, 1, 2]
Distinct values in order of first appearance (one NaN at most). Equivalent to R's
unique().