# How to remove duplicates in an array

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MKN on 2 Jul 2013
Ex: In the array x=[1 2 2 3 3 3 4 5], i want to eliminate all repeating elements (2,3) and retain non-repeating elements (1,4,5)
i.e., If x=[1 2 2 3 3 3 4 5], answer should be x=[1 4 5]

Octa on 2 Jul 2013
Edited: Octa on 2 Jul 2013
>> x=[1 2 2 3 3 3 4 5];
>> y = zeros(size(x));
>> for i = 1:length(x)
y(i) = sum(x==x(i));
end
>> for i=length(y):-1:1
if(y(i)>=2)
x(i)=[];
end
end
>>x
1 4 5
Jan on 2 Jul 2013
@Octa: Please do not post solutions of homework questions. Reducing the size of an array iteratively has a bad performance. An efficient and more matlabish approach for the 2nd loop:
x = x(x >= 2);

Image Analyst on 2 Jul 2013
Sounds like homework. As hints, I'd probably use max() to find the greatest integer and the histogram edges, histc() to get the counts, and ismember() to help with removal. It's just a few lines of code - see if you can do it.

Jan on 2 Jul 2013
You can also SORT the values at first and obtain the sorting index as 2nd output. Then use DIFF to find equal elements. Finally you can remove them and restore the original order by using the sorting index.