Modify Footnote Symbols

modify_footnote_symbol() customizes the symbols used to reference footnotes in a gtsummary table. By default, footnotes are referenced with sequential numbers (1, 2, 3, ...). This function replaces those numbers with a user-specified set of symbols, e.g. c("*", "\u2020", "\u2021") (an asterisk, dagger, and double dagger).
remove_footnote_symbol() resets the footnote reference marks back to the default numbering.

Usage

modify_footnote_symbol(x, symbol)

remove_footnote_symbol(x)

Arguments

x: (gtsummary)
A gtsummary object
symbol: (character)
a character vector of length 2 or greater giving the ordered symbols used to reference footnotes, e.g. c("*", "\u2020", "\u2021"). Symbols are assigned to footnotes in the order the footnotes appear in the table. When the number of footnotes exceeds the number of symbols supplied, the symbols are recycled. A length of at least 2 is required because as_gt() passes these to gt::opt_footnote_marks(), which interprets a single string as the name of a built-in mark scheme. Currently only utilized by as_gt() and as_flex_table().

Value

Updated gtsummary object

Details

The symbol sequence may also be set for all tables via the "pkgwide-chr:footnote_symbol" theme element; a value set with modify_footnote_symbol() takes precedence over the theme element.

Common footnote marks

The table below lists common footnote reference marks and the R strings used to create them. The six marks correspond to those used in gt::opt_footnote_marks(marks = "extended"). Pass the R string (e.g. "\u2020") to the symbol argument to obtain the corresponding mark.

Name	Unicode	R string
asterisk	`U+002A`	`"*"`
dagger	`U+2020`	`"\u2020"`
double dagger	`U+2021`	`"\u2021"`
section sign	`U+00A7`	`"\u00A7"`
double vertical line	`U+2016`	`"\u2016"`
pilcrow (paragraph sign)	`U+00B6`	`"\u00B6"`

Examples

# use symbols (instead of numbers) to reference footnotes
trial |>
  tbl_summary(by = trt, include = c(age, grade), missing = "no") |>
  add_p() |>
  modify_footnote_symbol(symbol = c("*", "\u2020", "\u2021"))


  Characteristic
      Drug A

N = 98^*
      Drug B

N = 102^*
      p-value^†
    
Age
46 (37, 60)
48 (39, 56)
0.7
Grade




0.9
    I
35 (36%)
33 (32%)

    II
32 (33%)
36 (35%)

    III
31 (32%)
33 (32%)

^* Median (Q1, Q3); n (%)
    
^† Wilcoxon rank sum test; Pearson’s Chi-squared test

Characteristic	Drug A N = 98^*	Drug B N = 102^*	p-value^†
Age	46 (37, 60)	48 (39, 56)	0.7
Grade			0.9
I	35 (36%)	33 (32%)
II	32 (33%)	36 (35%)
III	31 (32%)	33 (32%)
^* Median (Q1, Q3); n (%)
^† Wilcoxon rank sum test; Pearson’s Chi-squared test