How to compare elements of a 2D array with other elements of the same array.

I have an 2D array where I have to compare each element with all the others and save the index position if the two elements are equal.

How can I do that using lesser for loops?

I can't give the code for array here because it is a big data. Can you answer with an example.

Thanks .

Edit: Initial question might be unclear.

Just to give an example, suppose I have an array A:

A=[1 2 3 ; 2 9 5; 4 1 8]

Here A(1,1) and A(3,2) are both =1

I need to detect all of such pairs or collection of index(if more than two).

Answer 1

[KSSV]

You can use ismember. Read about the function ismember.

Answer 2

[Arif Hoq]

A=[1 2 3 ; 2 9 5;  4 1 8]

A = 3×3

1 2 3 2 9 5 4 1 8

[A1 C]=ismember(A(:),A);
A2=sort(C); % sorting index
A3=A(A2) % value of A those are identical

A3 = 9×1

1 1 2 2 4 9 3 5 8