TableCurve 2D

From Systat Software:

You can quickly find the best equations for your data. Fit all of TableCurve 2D 3,665 built-in equations or just the ones you need in seconds. With TableCurve 2D, a single mouse click is all it takes to start the automated curve fitting process, there is no set up required. Unlike most curve fitting programs, TableCurve 2D will automatically choose initial parameter estimates. Now you don't have to be mathematically inclined to find equations that describe data. TableCurve saves you precious time because it takes the endless trial and error out of curve fitting.

Up to 15 user-defined equations can be entered and ranked along with the built-in equations. These specialized models can contain most mathematical constructs, including special functions, series convergence and conditional statements, differentiations, integrations, and parameter constraints. You can also add up to 100 C or FORTRAN language functions to the TableCurve 2D equation set with unlimited complexity.