1. A method for determining an unknown valuation function, comprising the steps of: a computing device determining one or more first degree correlations based on valuation information; the computing device determining one or more important variables based on at least a comparison between an absolute value of the one or more first degree correlations and a first threshold value; the computing device determining one or more subsets of the determined one or more important variables, wherein each of the one or more subsets includes one or more variable combinations; the computing device determining that a first subset of the one or more subsets has a lowest additive approximation error among the one or more subsets; the computing device determining a multiplicative approximation error for each variable combination of the first subset; based on determining that the one or more variable combinations of the first subset have the acceptable multiplicative approximation error, the computing device determining a valuation function based on at least the first subset, wherein the valuation function is applicable to the one or more variable combinations of the first subset that have an acceptable multiplicative error.