fmt: Set a column format with a formatter function

Description

The fmt() function provides a way to execute custom formatting functionality with raw data values in a way that can consider all output contexts.

Along with the columns and rows arguments that provide some precision in targeting data cells, the fns argument allows you to define one or more functions for manipulating the raw data.

If providing a single function to fns, the recommended format is in the form: fns = function(x) .... This single function will format the targeted data cells the same way regardless of the output format (e.g., HTML, LaTeX, RTF).

If you require formatting of x that depends on the output format, a list of functions can be provided for the html, latex, rtf, and default contexts. This can be in the form of fns = list(html = function(x) ..., latex = function(x) ..., default = function(x) ...). In this multiple-function case, we recommended including the default function as a fallback if all contexts aren't provided.

Usage

fmt(data, columns = everything(), rows = everything(), fns, prepend = FALSE)

Value

An object of class gt_tbl.

Arguments

data: A table object that is created using the gt() function.
columns: The columns to format. Can either be a series of column names provided in c(), a vector of column indices, or a helper function focused on selections. The select helper functions are: starts_with(), ends_with(), contains(), matches(), one_of(), num_range(), and everything().
rows: Optional rows to format. Providing everything() (the default) 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 helper function focused on selections. The select helper functions are: 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).
fns: Either a single formatting function or a named list of functions.
prepend: Should the formatting function(s) be brought to the beginning of the formatting queue (TRUE) or placed at the end (FALSE). By default, this is FALSE and this leads to 'last-one-wins' semantics.

Examples

Use exibble to create a gt table. Format the numeric values in the num column with a function supplied to the fns argument.

exibble %>%
  dplyr::select(-row, -group) %>%
  gt() %>%
  fmt(
    columns = num,
    fns = function(x) {
      paste0("'", x * 1000, "'")
    }
  )

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

Function ID

3-16

Details

As with all of the fmt_*() functions, targeting of values is done through columns and additionally by rows (if nothing is provided for rows then entire columns are selected). Conditional formatting is possible by providing a conditional expression to the rows argument. See the Arguments section for more information on this.