1. A computer implemented method to find a mathematical equation that fits a data set having one dependent variable and at least one independent variable comprising determining the relative contribution of the at least one independent variable to the dependent variable, and defining separate functions that each describe the contribution of a single independent variable to the dependent variable, wherein the functions used to describe the contribution of an independent variable to the dependent variable are derived using residuals of the dependent variable, wherein the residuals comprise the portion of the dependent variable for which a contributing independent variable has not been defined.