R is a Boolean vector whose length is the number of major cells in Y. For each major cell of Y, the corresponding element of R is 1 if it is the first occurrence of that value, and 0 if it is a duplicate of an earlier major cell.
⎕CT and ⎕DCT are implicit arguments of Unique.
Examples
≠22 10 22 22 21 10 5 10 1 1 0 0 1 0 1 0
≠ v←'CAT' 'DOG' 'CAT' 'DUCK' 'DOG' 'DUCK'
1 1 0 1 0 0
⊢mat←↑v
CAT
DOG
CAT
DUCK
DOG
DUCK
≠mat
1 1 0 1 0 0