Format values as dates

Usage

fmt_date(
  data,
  columns = everything(),
  rows = everything(),
  date_style = "iso",
  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).

date_style

Predefined style for dates

scalar<character>|scalar<numeric|integer>(1<=val<=41) // default: "iso"

The date style to use. By default this is the short name "iso" which corresponds to ISO 8601 date formatting. There are 41 date styles in total and their short names can be viewed using info_date_style().

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 to 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_date() is compatible with body cells that are of the "Date", "POSIXt" or "character" 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_date() 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():

• date_style

• pattern

• locale

Please note that for each 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.

Formatting with the date_style argument

We need to supply a preset date style to the date_style argument. The date styles are numerous and can handle localization to any supported locale. A large segment of date styles are termed flexible date formats and this means that their output will adapt to any locale provided. That feature makes the flexible date formats a better option for locales other than "en" (the default locale).

The following table provides a listing of all date styles and their output values (corresponding to an input date of 2000-02-29).

We can call info_date_style() in the console to view a similar table of date styles with example output.

Adapting output to a specific locale

This formatting function can adapt outputs according to a provided locale value. Examples include "en" for English (United States) and "fr" for French (France). Note that a locale value provided here will override any global locale setting performed in gt()'s own locale argument (it is settable there as a value received by all other functions that have a locale argument). As a useful reference on which locales are supported, we can call info_locales() to view an info table.

Examples

Let's use the exibble dataset to create a simple, two-column gt table (keeping only the date and time columns). With fmt_date(), we'll format the date column to display dates formatted with the "month_day_year" date style.

exibble |>
  dplyr::select(date, time) |>
  gt() |>
  fmt_date(
    columns = date,
    date_style = "month_day_year"
  )

Again using the exibble dataset, let's format the date column to have mixed date formats, where dates after April 1st will be different than the others because of the expressions used in the rows argument. This will involve two calls of fmt_date() with different statements provided for rows. In the first call (dates after the 1st of April) the date style "m_day_year" is used; for the second call, "day_m_year" is the named date style supplied to date_style.

exibble |>
  dplyr::select(date, time) |>
  gt() |>
  fmt_date(
    columns = date,
    rows = as.Date(date) > as.Date("2015-04-01"),
    date_style = "m_day_year"
  ) |>
  fmt_date(
    columns = date,
    rows = as.Date(date) <= as.Date("2015-04-01"),
    date_style = "day_m_year"
  )

Use the exibble dataset to create a single-column gt table (with only the date column). Format the date values using the "yMMMEd" date style (which is one of the 'flexible' styles). Also, we'll set the locale to "nl" to get the dates in Dutch.

exibble |>
  dplyr::select(date) |>
  gt() |>
  fmt_date(
    date_style = "yMMMEd",
    locale = "nl"
  )

Function ID

3-13

Function Introduced

v0.2.0.5 (March 31, 2020)

See also