Aggregate gridded grass availability to polity totals.

Sums gridded grass availability to polity (country, or subnational where available) totals, splitting each cell's grass by the cell's land-area share in each polity so border cells are attributed proportionally. The polity grass supply ceiling for feed allocation.

Usage

aggregate_grass_to_polity(
  grass,
  cell_polity,
  polity_validity = c("keep", "flag", "drop")
)

Arguments

grass

Gridded grass availability from build_grass_availability(), with lon, lat, year and grass_avail_dm_t.

cell_polity

Cell-to-polity mapping with lon, lat, area_code and polity_frac (the cell's land-area fraction in the polity; pass 1 for a majority assignment, e.g. from country_grid).

polity_validity

What to do with a row whose (area_code, year) resolves to a polity that did not exist in that year (the cell-polity crosswalk has no year dimension, so an early-20th-century cell is labelled with its present-day territory). "keep" (default) keeps every row, which is the historical behaviour, and warns naming the rows, years and area codes involved. "flag" keeps them and adds the per-row logical reporting_polity_out_of_span, marking exactly which rows are stand-ins. "drop" removes them. All three warn; only "drop" changes the numbers. See polity_coverage_gaps(), which reports the same rows for an already-built table.

Value

A tibble with area_code, year and grass_avail_dm_t, plus reporting_polity_out_of_span when polity_validity = "flag". This output carries no reporting-polity columns, so the flag is attached directly rather than derived from them.

Examples

grass <- build_grass_availability(method = "lpjml", example = TRUE)
cp <- tibble::tibble(
  lon = grass$lon,
  lat = grass$lat,
  area_code = 1L,
  polity_frac = 1
)
aggregate_grass_to_polity(grass, cp)
#> # A tibble: 1 × 3
#>   area_code  year grass_avail_dm_t
#>       <int> <int>            <dbl>
#> 1         1  2000            45730