Execute dplyr operation only if column exists

Question

Drawing on the discussion on conditional dplyr evaluation I would like conditionally execute a step in pipeline depending on whether the reference column exists in the passed da

Answer 1

With across() in dplyr > 1.0.0 you can now use any_of when filtering. Compare original with all columns:

mtcars %>% 
  filter(am == 1) %>% 
  filter(cyl == 4)

With cyl removed, it throws an error:

mtcars %>% 
  select(!cyl) %>% 
  filter(am == 1) %>% 
  filter(cyl == 4)

Using any_of (note you have to write "cyl" and not cyl):

mtcars %>% 
  select(!cyl) %>% 
  filter(am == 1) %>% 
  filter(across(any_of("cyl"), ~.x == 4))
#N.B. this is equivalent to just filtering by `am == 1`.