The fmt_partsper() function

Create a tibble of small numeric values and generate a gt table. Format the a column to appear in scientific notation with fmt_scientific() and format the b column as per mille values with fmt_partsper().

dplyr::tibble(x = 0:-5, a = 10^(0:-5), b = a) |>
  gt(rowname_col = "x") |>
  fmt_scientific(a, decimals = 0) |>
  fmt_partsper(
    columns = b,
    to_units = "per-mille"
  )

	a	b
0	1	1,000.00‰
-1	1 × 10−1	100.00‰
-2	1 × 10−2	10.00‰
-3	1 × 10−3	1.00‰
-4	1 × 10−4	0.10‰
-5	1 × 10−5	0.01‰