Given a set of at least 180 data-points (dates as X and associated non-negative values as Y) - how would one go about predicting/forecasting future data-points?
I'm not even sure whether what I'm looking for is 'non-linear extrapolation', but searching on things like newton/lagrange, polynomial regression, etc - I just don't seem to be able to find one formula, but perhaps that's because it can't be simplified like that. I also read that it depends a lot on the data.
My data-points are prices that go up and down, and follow no mathematical equation, not random - and frequency, oscillation and so forth, are unknown. Is this possible to achieve? I'm not interested in using 3rd-party programs like Excel/Matlab, but rather develop the model. Thanks in advance.