Format values to indexed characters

With numeric values in a gt table we can transform those to index values, usually based on letters. These characters can be derived from a specified locale and they are intended for ordering (often leaving out characters with diacritical marks).

Usage

fmt_index(
  data,
  columns = everything(),
  rows = everything(),
  case = c("upper", "lower"),
  index_algo = c("repeat", "excel"),
  pattern = "{x}",
  locale = NULL
)

Arguments

data

The gt table data object

obj:<gt_tbl> // required

This is the gt table object that is commonly created through use of the gt() function.

columns

Columns to target

<column-targeting expression> // default: everything()

Can either be a series of column names provided in c(), a vector of column indices, or a select helper function (e.g. starts_with(), ends_with(), contains(), matches(), num_range() and everything()).

rows

Rows to target

<row-targeting expression> // default: everything()

In conjunction with columns, we can specify which of their rows should undergo formatting. The default everything() results in all rows in columns being formatted. Alternatively, we can supply a vector of row captions within c(), a vector of row indices, or a select helper function (e.g. starts_with(), ends_with(), contains(), matches(), num_range(), and everything()). We can also use expressions to filter down to the rows we need (e.g., [colname_1] > 100 & [colname_2] < 50).

case

Use uppercase or lowercase letters

singl-kw:[upper|lower] // default: "upper"

Should the resulting index characters be rendered as uppercase ("upper") or lowercase ("lower") letters? By default, this is set to "upper".

index_algo

Indexing algorithm

singl-kw:[repeat|excel] // default: "repeat"

The indexing algorithm handles the recycling of the index character set. By default, the "repeat" option is used where characters are doubled, tripled, and so on, when moving past the character set limit. The alternative is the "excel" option, where Excel-based column naming is adapted and used here (e.g., [..., Y, Z, AA, AB, ...]).

pattern

Specification of the formatting pattern

scalar<character> // default: "{x}"

A formatting pattern that allows for decoration of the formatted value. The formatted value is represented by the {x} (which can be used multiple times, if needed) and all other characters will be interpreted as string literals.

locale

Locale identifier

scalar<character> // default: NULL (optional)

An optional locale identifier that can be used for formatting values according the locale's rules. Examples include "en" for English (United States) and "fr" for French (France). We can call info_locales() for a useful reference for all of the locales that are supported. A locale ID can be also set in the initial gt() function call (where it would be used automatically by any function with a locale argument) but a locale value provided here will override that global locale.

Value

An object of class gt_tbl.

Compatibility of formatting function with data values

fmt_index() is compatible with body cells that are of the "numeric" or "integer" types. Any other types of body cells are ignored during formatting. This is to say that cells of incompatible data types may be targeted, but there will be no attempt to format them.

Compatibility of arguments with the `from_column()` helper function

from_column() can be used with certain arguments of fmt_index() to obtain varying parameter values from a specified column within the table. This means that each row could be formatted a little bit differently. These arguments provide support for from_column():

case
index_algo
pattern
locale

Please note that for all of the aforementioned arguments, a from_column() call needs to reference a column that has data of the correct type (this is different for each argument). Additional columns for parameter values can be generated with cols_add() (if not already present). Columns that contain parameter data can also be hidden from final display with cols_hide(). Finally, there is no limitation to how many arguments the from_column() helper is applied so long as the arguments belong to this closed set.

Examples

Using a summarized version of the towny dataset, let's create a gt table. Here, fmt_index() is used to transform incremental integer values into capitalized letters (in the ranking column). With cols_merge() that formatted column of "A" to "E" values is merged with the census_div column to create an indexed listing of census subdivisions, here ordered by increasing total municipal population.

towny |>
  dplyr::select(name, csd_type, census_div, population_2021) |>
  dplyr::group_by(census_div) |>
  dplyr::summarize(
    population = sum(population_2021),
    .groups = "drop_last"
  ) |>
  dplyr::slice_min(population, n = 5) |>
  dplyr::mutate(ranking = dplyr::row_number(), .before = 0) |>
  gt() |>
  fmt_integer() |>
  fmt_index(columns = ranking, pattern = "{x}.") |>
  cols_merge(columns = c(ranking, census_div)) |>
  cols_align(align = "left", columns = ranking) |>
  cols_label(
    ranking = md("Census  \nSubdivision"),
    population = md("Population  \nin 2021")
  ) |>
  tab_header(title = md("The smallest  \ncensus subdivisions")) |>
  tab_options(table.width = px(325))

This image of a table was generated from the first code example in the `fmt_index()` help file.

Function ID

3-10

Function Introduced

v0.9.0 (Mar 31, 2023)