CompuServe Messages

I downloaded the one called XYPlot, and it seems to be what I need. My only bugs are that the data can't be entered from within the program, and the method used to fit a curve doesn't really produce an accurate curve. For example, I entered some data from a physics lab; a plot of voltage vs resistance. The curve was supposed to go to zero, but the curve that was fitted started to climb back up at that point. I remember reading that you are a mathmatician. Do you know "a" formula that will use the points to figure out a curve that would fit the points? If you don't, which math would it be consider in? My College has plenty of textbooks I can poke around in, but I don't know where to start. I think I may try to develop a better graphing program. I have some ideas of what it should include. Although, I think by the time I finish it (or even get started) I won't have any purpose for it!