my_df <- tibble(
b1 = c(2, 1, 1, 2, 2, 2, 1, 1, 2),
b2 = c(NA, 4, 6, 2, 6, 6, 1, 1, 7),
b3 = c(5, 9, 8, NA, 2, 3, 9, 5, NA),
b4 = c(NA, 6, NA, 10, 12, 8, 3, 6, 2),
b5 = c(2, 12, 1, 7, 8, 5, 5, 6, NA),
b6 = c(9, 2, 4, 6, 7, 6, 6, 7, 9),
b7 = c(1, 3, 7, 7, 4, 2, 2,