To implement OO or not in R package, and if so, how to structure it?

Did you read this?
https://cran.r-project.org/doc/contrib/Leisch-CreatingPackages.pdf

Maybe it could give you some insight in how to create package.

That resource is ~9 years old. There are more modern treatments available. You
can read mine at http://r-pkgs.had.co.nz.

Hadley

Thanks both.  I'm reading through your new book now Hadley... thanks for 
that.  I'll probably take a shot at building a class to hold one tree 
per object, and search for objects of a class (per 
https://stackoverflow.com/questions/5158830/identify-all-objects-of-given-clas-for-further-processing) 
to implement collections when necessary...

It does seem like there might be niche out there for a resource for 
folks deciding how to structure their package given what they're trying 
to provide; i.e. should they construct a collection of functions, or 
class defs, or...  Could well exist already, and I may just have missed 
it...

Thanks,
Allie