A data processing system-implemented method or data processing system readable medium can be used to model operating parameter(s) for a vendor. Detailed analysis of the impact of prices or other variables, on the demand of each item, is performed. These allow us to prune large numbers of prices or other variables which have little or no impact on a given item. After determining which prices and other variables are significantly related to an item, a more in-depth examination of that small list of variables may be performed. This in-depth examination will result in a set of final weighing factors, quantifying the effect of each on the item. The weighing factors for all other variables can be assigned a value of zero. By limiting the number of non-zero weighing factors, the time needed to generate all the weighing factors for a matrix (or matrices) is reduced.