I don't have a copy of SV4 (or SV3, where model.frame was introduced), but
S+ 8.3 (based on SV4) puts the class "model.frame" on model.frame()'s
return value but has no methods (in the default packages) for class
"model.frame". Perhaps that is why R omitted the class.
However, S+ 8.3's (and probl
Dear Martin,
Since no one else has picked up on this, I’ll take a crack at it:
The proposal is to define the S3 class of model-frame objects as
c(“model.frame”, “data.frame”) (not the formal class of these objects, even
though this feature was coincidentally introduced in S4). That’s unlikely
