Eureqa is a program that takes data & attempts to find a function composed from a set of given functions by all manner of functional compositions; i.e., it isn't restricted to linear combinations or splines or anything that simple. This is _not_ Lagrange interpolation. You can download & run a free version from here: http://www.nutonian.com/ Ignore all of the instructions, and just go through the built-in example. First go to "Enter Data", where you see a bunch of data already entered. Then go to "Prepare Data", where you see the data already prepared. Then go to "Set Target", where you see the target already set. Then go to "Start Search" and hit the "Run" button to start the program searching. On Windows, you don't even have to "install" the program if you don't want to; you can download the .zip version onto a USB stick & execute the program from there. I'm just trying the program out. Eventually, I'd like to see if it can guess some anti-derivatives from evaluating the expressions at a sufficient number of points.