removing duplicates in an array

If i have the following array

a =[1,1,1,2,2,1,1,6,6,6,8,8,2,2,3,3,2,2]

When i do unique(a,'stable'), i get

[1,2,6,8,3]

I want the following result

[1,2,1,6,8,2,3,2]

Answer 1

[Stephan]

b = a(logical([1 (diff(a)~=0)]))

[Esegboria Osarhemen]

Thanks

[Jan]

(diff(a)~=0) is a logical vector. Concatenating it with a double converts it to a double. Casting it by logical() converts it again. More efficient:

b = a([true, diff(a)~=0])

Now the values are not converted twice.

Answer 2

[Brent F]

Using @Jan's idea, but:

• Package as a function
• Handle case where column-vector is given (return in same format as given)

function [uniqueSequence] = DedupSequence (seq)
    % Eliminate sequentially repeated rows
    
    % Create row vector for diff (must transpose if given a column vector)
    if size(seq,1) > 1
        seqCopy = seq(:,1)'; 
    else
        seqCopy = seq;
    end
    uniqueSequence = seq([true, diff(seqCopy)~=0]);
end