command unique without sorting??

196 vues (au cours des 30 derniers jours)
Nicoletta
Nicoletta le 25 Mar 2014
Commenté : Tom Toulouse le 26 Mai 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]

Réponses (4)

Honglei Chen
Honglei Chen le 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 le 26 Mar 2014
Modifié(e) : Andrei Bobrov le 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 le 25 Mar 2014
[vu,~,idx] = unique(v.','stable')
vs = accumarray(idx,ones(numel(v),1))
[vu vs]

Gabor
Gabor le 1 Mai 2021
Modifié(e) : Gabor le 1 Mai 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 commentaire
Tom Toulouse
Tom Toulouse le 26 Mai 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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