从 R 中的语言 object 中提取属性

Question

I fit a GLM model in R, and in the resulting model object, there is an element that is called 'terms'. The 'terms' object is an 'language' object.

I am not familiar with the 'language' object. I am wondering how I would be able to extract the 'attributes' from the model$terms object. For example, if I would like to get the 'predvars' attributes from this object, how should I do it?

> model = glm(...)

> typeof(model$terms)
[1] "language"

> model$terms
losscost_bc_fire_cap ~ pol_year_fac + ded_group + ind_score
attr(,"variables")
list(target, pol_year_fac, ded_group , ind_score)
......
attr(,"term.labels")
[1] "pol_year_fac"       "ded_bco_fire_group" "ind_grewscore"      "cv_grewscore"      
[5] "cv_log_tiv"        
attr(,"order")
[1] 1 1 1 1 1
attr(,"intercept")
[1] 1
attr(,"response")
[1] 1
attr(,".Environment")
<environment: R_GlobalEnv>
attr(,"predvars")
list(losscost_bc_fire_cap, pol_year_fac, ded_bco_fire_group, 
    ind_grewscore, cv_grewscore, cv_log_tiv)
attr(,"dataClasses")
losscost_bc_fire_cap         pol_year_fac   ded_bco_fire_group        ind_grewscore 
           "numeric"             "factor"             "factor"             "factor" 
        cv_grewscore           cv_log_tiv            (weights) 
           "numeric"            "numeric"            "numeric" 

Answer 1

Use the attr() function.

attr(model$terms, "predvars")

Or (I think) attributes(model$terms)$predvars

Watch out, though: the predvars is an unevaluated language object. You'll need to use eval() (or something) if you want to work with it.