The cropland each unit holds, on the basis the capacity ceiling uses

Sum a gridded cropland extent onto the units of an allocation layer, weighting every cell by cell_area_frac. This is the denominator reconcile_admin_allocation()'s implied cropping intensity divides by, and it is deliberately the same quantity .capacity_bases() multiplies by the multi-cropping factor: an intensity taken against any other land basis would not be comparable with the ceiling it is flagged against.

A physical cell shared by two units contributes its cropland to each in proportion, so the units' extents inside one cell add up to that cell's own cropland and nothing is double counted. Rows are selected per year by the layer's own validity convention, so an interval-keyed layer returns the unit that existed in each cropland year.

Usage

unit_cropland_extent(allocation_layer, gridded_cropland)

Arguments

allocation_layer

The country grid the allocation ran on, from build_allocation_layer(): lon, lat, area_code, cell_area_frac and, where a depth is granted, level_polity_code.

gridded_cropland

Per-cell cropland extent, as build_gridded_landuse() takes it: lon, lat, year, cropland_ha.

Value

A tibble of year, area_code, level_polity_code, cropland_ha and n_cells.

See also

reconcile_admin_allocation().

Examples

layer <- tibble::tibble(
  lon = c(0.25, 0.75, 0.75), lat = 50.25, area_code = 1L,
  level_polity_code = c("A1", "A1", "A2"), level = 1L,
  cell_area_frac = c(1, 0.25, 0.75)
)
cropland <- tibble::tibble(
  lon = c(0.25, 0.75), lat = 50.25, year = 2000L,
  cropland_ha = c(100, 400)
)
unit_cropland_extent(layer, cropland)
#> # A tibble: 2 × 5
#>    year area_code level_polity_code cropland_ha n_cells
#>   <int>     <int> <chr>                   <dbl>   <int>
#> 1  2000         1 A1                        200       2
#> 2  2000         1 A2                        300       1