To find the position of the elements which are same in vector

I have a vector like this: a = [ 2 3 4 2 5 4 3 3]; and I want to find all the index of the elements which has the same value. output like this: # 2, [1 4] # 3, [2 7 8] # 4, [3 6] # 5, [5]

Answer 1

[Matt Fig]

find(a==2)

[UTA]

but I have to search for a(1) to a(end), and that has duplicate ,how to simply this?

[Matt Fig]

Oh, well that's another thing.

a = [ 2 3 4 2 5 4 3 3];
[J,J] = histc(a,unique(a));
T = accumarray(J.',(1:length(J)).',[], @(x) {x});

Now T has the indices you seek.

Answer 2

[per isakson]

Try

    num = [ 2 3 4 2 5 4 3 3 ];
    unq = unique( num );
    ii  = arrayfun( @(x) find( num==x ), unq, 'uni', false ) ;

    >> unq
    unq =
         2     3     4     5
    >> ii{:}
    ans =
         1     4
    ans =
         2     7     8
    ans =
         3     6
    ans =
         5

or use a for-loop

Answer 3

[Javier]

 ind=unique(a)

 for i = 1 : length(ind);
 [z] =find(a==ind(i))
 limit(i,:)=[z(1) z(end)]
 end

   out = [ind limit]

regards