Didn’t mean to plug but you asked for it 
I’m working on this guide on formulas — it’s meant to teach you how to think about formulas so that you could write them like the one above. It’s not going very quickly though 
I haven’t raised too much for it so I had to still take client work to stay afloat. But whenever I have time I’m working on it, and I do hope to launch it (or at least some of it) by the end of this month.
The usual resources are the Formulas list and the official guides but I only remember seeing simple examples there.