Use a multidimensional array as a coordinate

[GillesC]

Given a 2D matrix of size AxB, I want to have a multidimensional coordinate associated to dimension "A".
For example, consider a 4D vector P of size AxRxRxR. I want to assign P as a coordinate to the dimension "A".

Another way to put it is, "Can you assign multiple coordinates to the same dimension"?

Is this possible?

Why I need this:
I want to have a position associated to each value along the A dimension. Given that we live in a 3D world, this requires 3 values per coordinate index.

Another option to do this is to go from the A dimension to AxRxRxR, but this would induce a lot of redundancy. And this is the answer I have found when searching for this problem.