How to delete elements that have repeats in arrays

Hey, i'm working on a problem where i have to check an array and delete all the elements that appear more than once in it. This is not what the unique function does(it leaves one copy of the repeated element) and i'm not sure if there's a function that does this, any ideas?

[Mickey]

sorry i should have given an example:

input=

2,3,4,4,5,6,2,2

output=

3,5,6

Answer 1

[Oleg Komarov]

Your original question is actually different from what you're trying to accomplish.

To remove duplicate rows:

[unV,locA,locB] = unique(v,'rows');
v(locA(histc(locB,1:size(unV,1)) == 1),:)

[Andrei Bobrov]

[uv, ~ ,ui] = unique(v,'rows')

out = uv(histc(ui,1:max(ui))==1,:)

Answer 2

[Walter Roberson]

For single row,

input= [2,3,4,4,5,6,2,2];
[b, i1] = unique(input,'first');
[b, i2] = unique(input,'last');
b(i1==i2);

For multi-rows, if it is unique rows you want to identify,

input = [2,3,4,5
 7,3,7,8
 2,4,2,1
 2,3,4,5
 5,6,3,2
 2,3,4,5];
[b, i1] = unique(input, 'rows', 'first');
[b, i2] = unique(input, 'rows', 'last');
b(i1==i2,:)

[Fangjun Jiang]

That's a good one, Walter! I was thinking that it could be solved using unique() and setdiff() or setxor() but couldn't figure it out.

Answer 3

[Friedrich]

Hi,

try this

input= [2,3,4,4,5,6,2,2];

un_in = unique(input);

n = hist(input,numel(un_in));

oputput = un_in(n==1)

[Oleg Komarov]

I would suggest to use histc since hist wraps around it.

Answer 4

[Mickey]

thanks, i should have given my example as a multiple row, multiple column array, but i figured it out anyway. here's what my answer looks like:

clear all
clc

v=[2,3,4,5
   7,3,7,8
   2,4,2,1
   2,3,4,5
   5,6,3,2
   2,3,4,5];

    j=0;

    n_rows= size(v,1);% Find number of rows in matrix

    for n = 1:n_rows %Check each row to see if is repeated 
        chk = ismember(v,v(n,:),'rows');% Find rows identical to row n 
        if sum(chk)>1 
            j=j+1;
            rep(j)=n; %row n has repeats, so store its index
        end
    end

    % Going in reverse order, ie from last row to first, delete repeat rows from array

    for tmp=j:-1:1
       y=rep(tmp);
       v(y,:)=[];
    end

v