Extract Predictor Names from Formula or Terms

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).

form_pred(object, ...)

Arguments

object	A model formula or stats::terms() object.
...	Arguments to pass to all.vars()

Value

A character vector of names

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"