Two questions:

1. How are pick() and c_across() different?
2. How do I make the second code block work? I can’t figure out how to combine the data types!

#Works
tibble(
  a_letter=sample(c(NA,"a","b"),size = 10,replace = T),
  a_number=sample(c(NA,1,2),size = 10,replace = T),
  hi="world"
) |> 
  rowwise() |> 
  mutate(empty_measurements=sum(is.na(pick(matches("a_")))))

#Does not work:
tibble(
  a_letter=sample(c(NA,"a","b"),size = 10,replace = T),
  a_number=sample(c(NA,1,2),size = 10,replace = T),
  hi="world"
) |> 
  rowwise() |> 
  mutate(empty_measurements=sum(is.na(pick(matches("a_")))))