Y may be any array. R is a vector of the unique major cells of Y (the unique items of a vector, the unique rows of a matrix and so forth), in the order in which they first appear in Y. For further information, see Major Cells.
⎕CT and ⎕DCT are implicit arguments of Unique.
Examples
∪ 22 10 22 22 21 10 5 10
22 10 21 5
∪ v←'CAT' 'DOG' 'CAT' 'DUCK' 'DOG' 'DUCK'
┌───┬───┬────┐
│CAT│DOG│DUCK│
└───┴───┴────┘
⊢mat←↑v
CAT
DOG
CAT
DUCK
DOG
DUCK
∪mat
CAT
DOG
DUCK
a←3 4 5⍴⍳20
a
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
∪a
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20