# Find values in list that appear exactly once

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Johannes Korsawe on 25 Aug 2017
Commented: Stephen23 on 17 Jul 2021
Hi there,
assume, i have a list of integer values. I need a fast way to find those values in the list, that appear exactly once.
By now i have a code that finds the duplicate values and dismisses them.
list = randi(100,100,1); % Generate a list which should contain duplicate values
[vals,i]=sort(list);
j=find(all(diff(vals)==0,2));
ii=i([j;j+1]);
list(ii)=[];
Is there a faster way to get the final result?
Cheers, Johannes

Stephen23 on 25 Aug 2017
Edited: Stephen23 on 25 Aug 2017
[tmp,idx] = sort(list);
idp = diff(tmp)>0;
list(idx([true;idp]&[idp;true]))
If you are okay with getting the output sorted then it can be simplified further:
tmp = sort(list);
idp = diff(tmp)>0;
tmp([true;idp]&[idp;true])
##### 3 CommentsShow 1 older commentHide 1 older comment
Mohammadreza Mahmoodi on 17 Jul 2021
what is idp means ?
Stephen23 on 17 Jul 2021
@Mohammadreza Mahmoodi: idp is a logical vector which indicates where the values change.

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