Align Column Numbers by Decimal Mark in gtsummary Table

Question

I am trying to create a table using the gtsummary package in R, with column numbers aligned by the decimal mark. Here's my code:

library(gtsummary)
library(gt)

theme_gtsummary_journal(journal = "jama")

gt::rx_adsl |>
  tbl_summary(
    include=c(SEX),
    by=TRTA,
    digits = all_categorical() ~ c(0, 1),
    missing = "no"
  )

This code produces the following table:

How can I modify the table so that the numbers in the columns are aligned by the decimal mark?

I tried using gtsummary::modify_table_styling, but I couldn't achieve the desired alignment by the decimal mark.

Desired result:

Answer 1

There are three things you need to do to get the alignment you are after.

1. Use formatting functions/rounding that include padding before the number to ensure all results are the same width. I am using the {cards} package for this, but you don't have to.
2. Change the cell alignment from center to right.
3. Use a fixed-width font for your table.

Example below!

library(gtsummary)
packageVersion("gtsummary")
#> [1] '1.7.2'

# the cards pkg has functions that have fixed-width formatting (with space padding)
# you don't need to use this package, however. It's not too much work to do it yourself
packageVersion("cards")
#> [1] '0.1.0'

tbl <- gt::rx_adsl |>
  tbl_summary(
    include = SEX,
    by = TRTA,
    # use formatting/rounding functions that include padding
    digits = all_categorical() ~ list(cards::alias_as_fmt_fn("xx"), 
                                      cards::alias_as_fmt_fn("xx.x%")),
    missing = "no"
  ) |> 
  # change from center to right alignment
  modify_column_alignment(all_stat_cols(), "right") |> 
  as_gt() |> 
  # lastly, you need to use a fixed-width font to get proper alignment
  gt::opt_table_font(
    stack = "monospace-slab-serif"
  )
#> 2 observations missing `TRTA` have been removed. To include these observations, use `forcats::fct_na_value_to_level()` on `TRTA` column before passing to `tbl_summary()`.

^{Created on 2024-05-16 with reprex v2.1.0}