The cells_summary() function

Use countrypops to create a gt table. Add some styling to the summary data cells with with tab_style(), using cells_summary() in locations.

countrypops |>
  dplyr::filter(country_name == "Japan", year < 1970) |>
  dplyr::select(-contains("country")) |>
  dplyr::mutate(decade = paste0(substr(year, 1, 3), "0s")) |>
  gt(
    rowname_col = "year",
    groupname_col = "decade"
  ) |>
  fmt_number(
    columns = population,
    decimals = 0
  ) |>
  summary_rows(
    groups = "1960s",
    columns = population,
    fns = list("min", "max"),
    fmt = ~ fmt_integer(.)
  ) |>
  tab_style(
    style = list(
      cell_text(style = "italic"),
      cell_fill(color = "lightblue")
    ),
    locations = cells_summary(
      groups = "1960s",
      columns = population,
      rows = 1
    )
  ) |>
  tab_style(
    style = list(
      cell_text(style = "italic"),
      cell_fill(color = "lightgreen")
    ),
    locations = cells_summary(
      groups = "1960s",
      columns = population,
      rows = 2
    )
  )

	population
1960s
1960	93,216,000
1961	94,055,000
1962	94,933,000
1963	95,900,000
1964	96,903,000
1965	97,952,000
1966	98,851,000
1967	99,879,000
1968	101,011,000
1969	102,219,000
min	93,216,000
max	102,219,000