R: Format by simply passing data through

fmt_passthrough {gt}

R Documentation

Format by simply passing data through

Description

We can format values with fmt_passthrough(), which does little more than: (1) coercing to character (as all the ⁠fmt_*()⁠ functions do), and (2) applying decorator text via the pattern argument (the default is to apply nothing). This formatting function is useful when don't want to modify the input data other than to decorate it within a pattern.

Usage

fmt_passthrough(
  data,
  columns = everything(),
  rows = everything(),
  escape = TRUE,
  pattern = "{x}"
)

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`).
`escape`	Text escaping `⁠scalar<logical>⁠` // default: `TRUE` An option to escape text according to the final output format of the table. For example, if a LaTeX table is to be generated then LaTeX escaping would be performed during rendering. By default this is set to `TRUE` but setting as `FALSE` would be useful in the case where text is crafted for a specific output format in mind.
`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.

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.

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

from_column() can be used with certain arguments of fmt_passthrough() 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():

escape
pattern

Please note that for both 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

Let's use the exibble dataset to create a single-column gt table (with only the char column). Now we can pass the data in that column through the 'non-formatter' that is fmt_passthrough(). While the the function doesn't do any explicit formatting it has a feature common to all other formatting functions: the pattern argument. So that's what we'll use in this example, applying a simple pattern to the non-NA values that adds an "s" character.

exibble |>
  dplyr::select(char) |>
  gt() |>
  fmt_passthrough(
    rows = !is.na(char),
    pattern = "{x}s"
  )

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

Function ID

3-28

Function Introduced

v0.2.0.5 (March 31, 2020)