Automatically format column data according to their values

The fmt_auto() function will automatically apply formatting of various types in a way that best suits the data table provided. The function will attempt to format numbers such that they are condensed to an optimal width, either with scientific notation or large-number suffixing. Currency values are detected by currency codes embedded in the column name and formatted in the correct way. Although the functionality here is comprehensive it's still possible to reduce the scope of automatic formatting with the scope argument and also by choosing a subset of columns and rows to which the formatting will be applied.

Usage

fmt_auto(
  data,
  columns = everything(),
  rows = everything(),
  scope = c("numbers", "currency"),
  lg_num_pref = c("sci", "suf"),
  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. Examples of select helper functions include starts_with(), ends_with(), contains(), matches(), one_of(), 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. Examples of select helper functions include starts_with(), ends_with(), contains(), matches(), one_of(), 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).

scope

Scope of automatic formatting

mult-kw:[numbers|currency] --- default: c("numbers", "currency")

By default, the function will format both "numbers"-type values and "currency"-type values though the scope can be reduced to a single type of value to format.

lg_num_pref

Large-number preference

singl-kw:[sci|suf] --- default: "sci"

When large numbers are present, there can be a fixed preference toward how they are formatted. Choices are scientific notation for very small and very large values ("sci"), or, the use of suffixed numbers ("suf", for large values only).

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 use the info_locales() function as 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.

Targeting cells with `columns` and `rows`

Targeting of values is done through columns and additionally by rows (if nothing is provided for rows then entire columns are selected). The columns argument allows us to target a subset of cells contained in the resolved columns. We say resolved because aside from declaring column names in c() (with bare column names or names in quotes) we can use tidyselect-style expressions. This can be as basic as supplying a select helper like starts_with(), or, providing a more complex incantation like

where(~ is.numeric(.x) && max(.x, na.rm = TRUE) > 1E6)

which targets numeric columns that have a maximum value greater than 1,000,000 (excluding any NAs from consideration).

By default all columns and rows are selected (with the everything() defaults). Cell values that are incompatible with a given formatting function will be skipped over, like character values and numeric fmt_*() functions. So it's safe to select all columns with a particular formatting function (only those values that can be formatted will be formatted), but, you may not want that. One strategy is to format the bulk of cell values with one formatting function and then constrain the columns for later passes with other types of formatting (the last formatting done to a cell is what you get in the final output).

Once the columns are targeted, we may also target the rows within those columns. This can be done in a variety of ways. If a stub is present, then we potentially have row identifiers. Those can be used much like column names in the columns-targeting scenario. We can use simpler tidyselect-style expressions (the select helpers should work well here) and we can use quoted row identifiers in c(). It's also possible to use row indices (e.g., c(3, 5, 6)) though these index values must correspond to the row numbers of the input data (the indices won't necessarily match those of rearranged rows if row groups are present). One more type of expression is possible, an expression that takes column values (can involve any of the available columns in the table) and returns a logical vector. This is nice if you want to base formatting on values in the column or another column, or, you'd like to use a more complex predicate expression.

Examples

Use the exibble dataset to create a gt table. Format all of the columns automatically with the fmt_auto() function.

exibble |>
  gt() |>
  fmt_auto()

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

Let's now use the countrypops dataset to create another gt table. We'll again use fmt_auto() to automatically format all columns but this time the choice will be made to opt for large-number suffixing instead of scientific notation. This is done by using the lg_num_pref = "suf" option.

countrypops |>
  dplyr::select(country_code_3, year, population) |>
  dplyr::filter(country_code_3 %in% c("CHN", "IND", "USA", "PAK", "IDN")) |>
  dplyr::filter(year > 1975 & year %% 5 == 0) |>
  tidyr::spread(year, population) |>
  dplyr::arrange(desc(`2020`)) |>
  gt(rowname_col = "country_code_3") |>
  fmt_auto(lg_num_pref = "suf")

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

Function ID

3-23

Function Introduced

v0.9.0 (Mar 31, 2023)