Polynomial Logarithmic Regression. The BTC cycle tops and bottoms were separately fit using a polynomial regression. The extensions are linear; meaning the extensions will overestimate the future top and bottom bands. The bottom band was fit on much more data than the top band, so is likely to be more reliable. The shape of the regression into the future was estimated, so may not be accurate into the future.
Use this indicator at your own risk. I make no claims as to its accuracy in forecasting future tops or bottoms of bitcoin.
This is used in the "BBI - Bitcoin Bottom Indicator," "BTI - Bitcoin Top Indicator", and the "BTB - Bitcoin Top and Bottom Indicator". Please see these indicators for more information as to how to support me developing more indicators in my spare time.
Would you be willing to share part of the code of your indicator? I've been working on a power law indicator and I would like to project the power law into the future Kind of like you've done here and I can't seem to get it quite right any help would be appreciated.