If you really want to work with hexagonal-shape cells, then I suggest the following:
1. Set the number of LTE_config.nr_eNodeB_rings=1;
2. Set the parameter LTE_config.compute_only_center_users = true; -> with this you will get the results only for the UEs assigned to the center eNodeB
3. To avoid the calculation of interference from interfering eNodeBs in your results, you could set the parameter there_are_interferers = false; Set this parameter at +network_elements/UEs.m inside the function “function link_quality_model_v1(obj,config)”, after the execution of obj.get_signal_macroscale_losses; basically you have to overwrite the parameter there_are_interferer and set it to false.
This is the easiest approach to achieve what you asked for. If you still want to modify ROI, I can give you more hints on that.