Weighted Sum Aggregation in a Simple Hierarchy. This diagram shows a simple hierarchy with four children and one parent value. Three of the children have values, while the fourth is empty. This empty cell has a null or NA value. Each cell has a weight value assigned to it, which changes the value. The first cell has a value of 2 and a weight of 3, giving it a calculated value of 6. The second cell has a value of 4 and a weight of 2, giving it a calculated value of 8. The third cell has a value of 6 and a weight of NA, giving it a calculated value of 6 because an NA weight value is calculated as a 1. The fourth cell is NA with a weight of 4, giving it a calculated value of NA. The calculated values have a total sum of 20.