All calculations are explained in the code.
The index is mainly based upon the components of the popular fear and greed index website. I've annotated the components in the code for you to look at.
If you're interested, you can replace the final variable 'Total' (within the 'barcolor' function at the very end) with any of the final outputs of the subcomponents to see the results of that single part.
Red = Greed
Green = Fear
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.