NLREG performs nonlinear regression and curve fitting. It fits a mathematical function whose form you specify to a set of data values. Virtually any type of function can be fitted. It includes a programming language similar to C that you use for describing the function to be fitted. Two dimensional line and three dimensional surface plots can be generated. The programming language includes a large selection of built-in library functions (sin, cos, log, exp, etc.) that makes it easy to describe complicated models.