While all.vars() returns all variables used in a formula, this
function only returns the variables explicitly used on the
right-hand side (i.e., it will not resolve dots unless the
object is terms with a data set specified).
Arguments
- object
A model formula or
stats::terms()object.- ...
Arguments to pass to
all.vars()
Examples
form_pred(y ~ x + z)
#> [1] "x" "z"
form_pred(terms(y ~ x + z))
#> [1] "x" "z"
form_pred(y ~ x + log(z))
#> [1] "x" "z"
form_pred(log(y) ~ x + z)
#> [1] "x" "z"
form_pred(y1 + y2 ~ x + z)
#> [1] "x" "z"
form_pred(log(y1) + y2 ~ x + z)
#> [1] "x" "z"
# will fail:
# form_pred(y ~ .)
form_pred(terms(mpg ~ (.)^2, data = mtcars))
#> [1] "cyl" "disp" "hp" "drat" "wt" "qsec" "vs" "am" "gear" "carb"
form_pred(terms(~ (.)^2, data = mtcars))
#> [1] "mpg" "cyl" "disp" "hp" "drat" "wt" "qsec" "vs" "am" "gear"
#> [11] "carb"