export_all_countries_summaries_xls: Export all countries summaries to Excel
In ElliottMess/rapporteur: Reports on triple billion data

export_all_countries_summaries_xls Export summaries of all countries for the three billions or for a specific billion.

export_all_countries_summaries_xls(
  df,
  billion = c("hpop", "hep", "uhc", "all"),
  year = "year",
  iso3 = "iso3",
  ind = "ind",
  value = "value",
  transform_value = "transform_value",
  scenario = NULL,
  type_col = "type",
  source_col = "source",
  population = "population",
  contribution = "contribution",
  contribution_pct = paste0(contribution, "_percent"),
  contribution_pct_total_pop = paste0(contribution, "_percent_total_pop"),
  default_scenario = "default_scenario",
  start_year = 2018,
  end_year = 2019:2025,
  output_folder = "outputs"
)

`df`	Data frame in long format, where 1 row corresponds to a specific country, year, and indicator.
`billion`	Billion indicator names to return, either "hep", "hpop", "uhc" , or "all".
`year`	Column name of column with years.
`iso3`	Column name of column with country ISO3 codes.
`ind`	Column name of column with indicator names.
`value`	Column name of column with indicator values.
`transform_value`	Column name of column(s) with transformed indicator values, used to calculate contributions.
`scenario`	Column name of column with scenario identifiers. Useful for calculating contributions on data in long format rather than wide format.
`type_col`	Column name of column with type data.
`source_col`	Column name of column to store source information.
`population`	Column name of column with population figures.
`contribution`	Column name of column(s) to store contribution (population) values. Must be the same length as `transform_value`.
`contribution_pct`	Column name of column(s) to store contribution (percent) values. Must be the same length as `transform_value`.
`contribution_pct_total_pop`	Column name of column(s) to store contribution (percent of total population of the country) values. Must be the same length as `transform_value`.
`default_scenario`	name of the default scenario.
`start_year`	Base year for contribution calculation, defaults to 2018.
`end_year`	End year(s) for contribution calculation, defaults to 2019 to 2025.
`output_folder`	Folder path to where the Excel files should be written