A method includes receiving, by a controller, a set of data. The set of data includes data of at least one explanatory variable and data of at least one response variable. The method also includes receiving, by the controller, an input that identifies a relevant explanatory variable. The method also includes generating, by the controller, an output data that corresponds to a symbolic expression that represents a relationship between the at least one explanatory variable and the at least one response variable. The symbolic expression is responsive to the identified relevant explanatory variable, and the symbolic expression includes a mathematically stable expression.