# removing duplicates in an array

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Esegboria Osarhemen on 3 Mar 2019
Edited: Brent F on 10 Jun 2021
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]

Stephan on 3 Mar 2019
b = a(logical([1 (diff(a)~=0)]))
##### 2 CommentsShowHide 1 older comment
Jan on 4 Mar 2019
(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.

Brent F on 10 Jun 2021
Edited: Brent F on 10 Jun 2021
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