There are many R functions out there but only some of them have a standard formula interface (see e.g. this question: Formula interface for glmnet). I think in general formula interfaces are a good way to standardize R functions and provide a consistent user experience.
My question
Is there an authoritative reference how to build a formula interface for a given R function and/or can you give an overview of the steps to do this? I hope that you don't have to program everything from scratch... Thank you