Chop It: Look up the Generating Data Frame Columns of a Formula Term

We the moody Gucci, Louis and Pucci men
Escada, Prada
The chopper it got the Uzi lens
Bird’s-eye view
The birds I knew, flip birds
Bird gangs, it was birds I flew

I want to be able to map the single formula term x1:x2 to the two
‘generating’ columns dat_foo[,c('x1','x2')]

In words, for a term in a ?formula, lookup the involved ‘root’ columns of the data frame inside the formula’s associated environment.

I feel like this mapping must exist under the lm() hood somewhere. Various stackoverflow Q+A’s about formulas never directly talk about this lookup. This Rviews blog post sums up the formula landscape pretty well. But there does not seem to be a convenient expose of the explicit lookup/hash table of the df to term mapping.

I have to hand roll the few lines of code to implement the hash / lookup table myself. My solution is ‘loose’ since it chops up the terms in the formula, then creates many sub-formulas for each chopped term.

After digging deeper, seems like you must still hand-roll a solution. There’s no single function/attribute that does this.

Found out there’s a weird difference between attributes(terms(formula(mod))) vs attributes(terms(mod))

attr(terms((mod1)),"dataClasses") # gives something close to initial goal

attr(terms(formula(mod1)),"dataClasses") # nothing

Reproducible Example Below as a followup to Ben Bolker’s suggestions