Get underlying row index for gt tables

Provides underlying row index for grouped or ungrouped gt tables. In some cases the visual representation of specific rows is inconsistent with the "row number" so this function provides the final output index for subsetting or targetting rows.

Usage

get_row_index(gt_object)

Arguments

gt_object

an existing gt table

Value

a vector of row indices

Examples

Create a helper function

This helper functions lets us be a bit more efficient when showing the row numbers/colors.

library(gt)

row_sty <- function(tab, row){

  OkabeIto <- c("#E69F00", "#56B4E9", "#009E73", "#F0E442",
                "#0072B2", "#D55E00", "#CC79A7", "#999999")
  tab %>%
    tab_style(
      cell_fill(color = OkabeIto[row]),
      locations = cells_body(rows = row)
    )
}

Randomize the data

We will randomly sample the data to get it in a specific order.

set.seed(37)
df <- mtcars %>%
  dplyr::group_by(cyl) %>%
  dplyr::slice_sample(n = 2) %>%
  dplyr::ungroup() %>%
  dplyr::slice_sample(n = 6) %>%
  dplyr::mutate(row_id = dplyr::row_number(), .before = 1)

#> df
#> A tibble: 6 × 12
#> row_id  mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
#> <int>  <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#>   1    10.4   8    472    205  2.93  5.25  18.0     0     0     3     4
#>   2    18.1   6    225    105  2.76  3.46  20.2     1     0     3     1
#>   3    21.4   6    258    110  3.08  3.22  19.4     1     0     3     1
#>   4    13.3   8    350    245  3.73  3.84  15.4     0     0     3     4
#>   5    33.9   4     71.1  65   4.22  1.84  19.9     1     1     4     1
#>   6    22.8   4    108    93   3.85  2.32  18.6     1     1     4     1

Ungrouped data

Ungrouped data works just fine, and the row indices are identical between the visual representation and the output.

gt(df) %>%
  row_sty(1) %>%
  row_sty(3) %>%
  row_sty(5)

Grouped data

However, for grouped data, the row indices are representative of the underlying data before grouping, leading to some potential confusion.

tab2 <- gt(df, groupname_col = "cyl")

tab2 %>%
  row_sty(1) %>% ## actually row 1
  row_sty(3) %>% ## actually row 5
  row_sty(5)     ## actually row 2

The get_row_index() function gives ability to create an index of the final output, so you can reference specific rows by number.

tab_index <- get_row_index(tab2)

tab2 %>%
  row_sty(4) %>% ## wrong row, actually row 6 visually
  row_sty(tab_index[4]) ## correct row, actually row 4

tab2 %>%
  row_sty(tab_index[1]) %>%
  row_sty(tab_index[3]) %>%
  row_sty(tab_index[5])