Are there any really good non linear regression calculators around the web? Or is something like MATLAB the best solution?
I tried using excel and its solver tool, but it's complete garbage lol. Granted, my modeling formula could be better, but there's got to be something better out there.
I used the model equation: $\mathrm{value}(t) = Ae^{-bt}\cos((\omega)(t)+(\varphi)) + y\text{-intercept} + m(t)$, where $m$ is a slope used in attempt to match the shape of this graph
Here's what I got from excel
Any ideas what tool I can use for a more accurate regression?