Allow variable x/y variables in bi_class

[kmcd39]

Hi!

It'd be awesome to be able to allow variable names in the bi_class function, to use this in more programmatic or interactive contexts in which the variables are not known in advance.

Regex:

# a working example w/ column names passed on directly
bicars <-
  tibble(cars) %>%
  biscale::bi_class(
     x = speed
    ,y = dist
    ,style = "equal"
  )

bicars # that works

# an example that doesn't work, where variables represent the same column names
first.column <- "speed"
second.column <- "dist"

tibble(cars) %>%
  biscale::bi_class(
    x = first.column
    ,y = second.column
    ,style = "equal"
  )

The second example doesn't work with !!, rlang::sym, or !!rlang::sym wrapping the variable column names either. It seems the as.character(substitute(.x)) freezes the evaluation? If there is a way to do this, including in the documentation would be helpful.

Thank you!