Thanks Carlie! Just to be clear on the concept of aggregation matrix when converting a fine grid to coarse grid, I made a diagram:
The fine source grid A cell# 11 would provide value for the coarse grid B cell#1 in the aggregation matrix? As an example, I would need to write a script that would only select row 2, col 1 cell from the entire collection of 9 grid-cells in source grid A for the aggregation matrix in grid cell# 1 target grid B - I am understanding it correctly?