command unique without sorting??

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Nicoletta
Nicoletta on 25 Mar 2014
Commented: Tom Toulouse on 26 May 2021
i need to delete the double numbers in a vector and create a new vector without the doubles and maintaining the same order... i used unique but i dont know how to let them stay in the same order! for exemple for
v=[7 6 3 3 2 3 5 2 2 4 1 4]
it should be
v=[7 6 3 2 5 4 1]

Answers (4)

Honglei Chen
Honglei Chen on 26 Mar 2014
You changed your question from yesterday, please don't do so. As to your new question, my answer above already covered it.
unique(v,'stable')

Andrei Bobrov
Andrei Bobrov on 26 Mar 2014
Edited: Andrei Bobrov on 26 Mar 2014
for older releases of Matlab
[~,b] = unique(v,'first')
a_out = v(sort(b))
or
[a0,b0,c0] = unique(v,'first')
[~,ii] = sort(b)
[~,jj] = sort(ii);
a_out = a0(ii);
b_out = b0(ii);
c_out = jj(c);

Honglei Chen
Honglei Chen on 25 Mar 2014
[vu,~,idx] = unique(v.','stable')
vs = accumarray(idx,ones(numel(v),1))
[vu vs]

Gabor
Gabor on 1 May 2021
Edited: Gabor on 1 May 2021
In my opinion unique should be "stable" by default. If someone wants to sort, than there is sort commant that for. What does sorting by default in unique has to do with removing duplicate values? In same logic why doesnt sorting has default unique function built in? Or do I missing any point? For me it does not make any sense nor being logical.
  1 Comment
Tom Toulouse
Tom Toulouse on 26 May 2021
It is because the 'stable' option did not exist on the first release of the unique function. Furthermore the simpliest way to get unique value is to sort the vector. So the stable option should be a little bit longer to execute.

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