The only way I'm aware of you have arrays within another indexed structure is to use cells. I'm not sure exactly what you are trying to do, but something like this should get you started:
I{1,1} = [1,3];
I{2,1} = [2,3];
I{1,2} = [1,4];
I{2,2} = [2,4];
This builds your initial cell array. Do what you want after that. Note that when using cells, the individual arrays are not linked by any means, so they can be different sizes and contain completely different data. You will have to control how each array grows and changes.
