I have got a curved line that I would like to find the equation of using Microsoft Excel. The curve seems to be either a polynomial or some sort of a trig graph. I've done some research and looked at regressions and things like that, but I don't quite understand how to use them properly and the results that actually come out. How would you do non-linear regeression (or use some other Excel tool) and how would you interpret/make sense of the "summary of results" (i.e. R² values, confidence range etc)?
By the way, I am a high school student, if that helps in identifying the level of explanation required.
Best Answer
You can always select a curve that passes through all the points (see for an example Lagrange interpolation), but that does no good, the curve might oscillate wildly between the points.
You have to conjecture some form of dependence between the variables. Perhaps out of an approximate model of the underlying phenomenon, by looking at a graph of the data, perhaps using different axes (linear, log-linear, log-log). Once you have settled on the correct form, you can fit the coefficients in it.