I have a two dim array. Example

what I am trying to say is array looks like these

0 1 2

3 4 5
6 7 8.....and so on.

The variable x will hold the values group by column id i.e when you debug the code, you can see it has 3 elements with id as 0 (which holds sequence as 0,3,6) , id as 1 (sequence 1,4,7) and so on.

In your case you know that it is index 2 so you can directly query the x[2]. Please let me know if you are still not clear about it.

Sorry bit I did not get what you meant by group arrayby columns?

That is first statement that you wrote?

Assume that you have 2D array k like {0,1,2,3,4,5,6,7,8,9,.....}

You can first group the array by columns as below.

and later, you can try finding the maximum of second dimension.