Redistribution of totals through hierarchical data
Adrian Smith · ACM SIGAPL APL Quote Quad · 2000
The early days of APL are full of examples of spreadsheet-style applications which allow the user to maintain aggregated values and quickly redistribute the changes across base data. Generally these use a simple pro-rata approach which always leads to rounding problems where the adjusted values no longer sum to the required total.The example discussed in this paper was developed for the Strategic Planning manager at Nestlé-Rowntree and a key requirement was to permit rebalancing of adjusted totals throughout an arbitrarily deep tree-structure. In this case a simple pro-rata leads to endless imbalances, and the trick is to use Benkard's distributed rounding which ensures that when changes to aggregates are redistributed, the detail always adds exactly to the required total.The concept is illustrated using the VideoSoft Flexgrid OCX control. The Flexgrid was used here because it has a very simple and powerful approach to managing gridded data where one of the dimensions has an outline structure.