R: Reference a column of values for certain parameters

from_column {gt}

R Documentation

Reference a column of values for certain parameters

Description

It can be useful to obtain parameter values from a column in a gt for functions that operate on the table body and stub cells. For example, you might want to indent row labels in the stub. You could call tab_stub_indent() and indent different rows to various indentation levels. However, each level of indentation applied necessitates a new call of that function. To make this better, we can use indentation values available in a table column via the from_column() helper function. For the tab_stub_indent() case, you'd invoke this helper at the indent argument and specify the column that has the values.

Usage

from_column(column, na_value = NULL, fn = NULL)

Arguments

column

Column name

⁠scalar<character>⁠ // required

A single column name in quotation marks. Values will be extracted from this column and provided to compatible arguments.

na_value

Default replacement for NA values

⁠scalar<character|numeric|logical>⁠ // default: NULL (optional)

A single value to replace any NA values in the column. Take care to provide a value that is of the same type as the column values to avoid any undesirable coercion.

fn

Function to apply

⁠function|formula⁠ // default: NULL (optional)

If a function is provided here, any values extracted from the table column (except NA values) can be mutated.

Value

A list object of class gt_column.

Functions that allow the use of the `from_column()` helper

Only certain functions (and furthermore a subset of arguments within each) support the use of from_column() for accessing varying parameter values. These functions are:

Within help documents for each of these functions you'll find the Compatibility of arguments with the from_column() helper function section and sections like these describe which arguments support the use of from_column().

Examples

from_column() can be used in a variety of formatting functions so that values for common options don't have to be static, they can change in every row (so long as you have a column of compatible option values). Here's an example where we have a table of repeating numeric values along with a column of currency codes. We can format the numbers to currencies with fmt_currency() and use from_column() to reference the column of currency codes, giving us values that are each formatted as having a different currency.

dplyr::tibble(
  amount = rep(30.75, 6),
  curr = c("USD", "EUR", "GBP", "CAD", "AUD", "JPY"),
) |>
  gt() |>
  fmt_currency(currency = from_column(column = "curr"))

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

Let's summarize the gtcars dataset to get a set of rankings of car manufacturer by country of origin. The n column represents the number of cars a manufacturer has within this dataset and we can use that column as a way to size the text. We do that in the tab_style() call; the from_column() function is used within the cell_text() statement to fashion different font sizes from that n column. This is done in conjunction with the fn argument of from_column(), which helps to tweak the values in n to get a useful range of font sizes.

gtcars |>
  dplyr::count(mfr, ctry_origin) |>
  dplyr::arrange(ctry_origin) |>
  gt(groupname_col = "ctry_origin") |>
  tab_style(
    style = cell_text(
      size = from_column(
        column = "n",
        fn = function(x) paste0(5 + (x * 3), "px")
      )
    ),
    locations = cells_body()
  ) |>
  tab_style(
    style = cell_text(align = "center"),
    locations = cells_row_groups()
  ) |>
  cols_hide(columns = n) |>
  tab_options(column_labels.hidden = TRUE) |>
  opt_all_caps() |>
  opt_vertical_padding(scale = 0.25) |>
  cols_align(align = "center", columns = mfr)

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

Function ID

8-5

Function Introduced

v0.10.0 (October 7, 2023)