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Split a cell-crop's production between its rainfed and irrigated regimes.

Source: R/regime_yield_ratio.R
split_regime_yield.Rd

Applies the irrigated:rainfed yield ratio R of build_regime_yield_ratio() to a cell-crop's production P and its rainfed and irrigated harvested areas A_r, A_i, keeping the production: Y_r = P / (A_r + R * A_i) and Y_i = R * Y_r, so A_r * Y_r + A_i * Y_i = P.

R starts from ratio_unbounded and two plausibility bounds can lower it, never below 1. The result is the output's ratio, the only ratio fit to weight anything:

  • Irrigated-yield ceiling. Where Y_i would exceed the item's Y_max, R is lowered until Y_i = Y_max, R = Y_max * A_r / (P - Y_max * A_i). Y_max is the 99th percentile of the item's national yields (production over harvested area) in get_primary_production(), pooled over countries and the years 1961-2023.

  • Rainfed-yield floor. Where Y_r would fall below the item's Y_min, the 1st percentile of the same pool, R is lowered until Y_r = Y_min, R = (P - Y_min * A_r) / (Y_min * A_i).

Lowering R raises Y_r and lowers Y_i, so the floor, applied after the ceiling, cannot break it. An item with no FAOSTAT yields of its own takes the pooled yields of the items that directly carry one of its SPAM crops in regime_yield_crop_mapping (spam_basis "direct" or "direct_aggregate"), stamped "bound_via_spam_crop".

A cell-crop with area in one regime only is a trivial split: all its production is on that regime, no ratio applies (ratio is 1, whatever ratio_unbounded is) and the bounds are not tested. Only a cell-crop with no area at all, or with both regimes and no ratio_unbounded, gets NA.

Usage

split_regime_yield(cells, bound = c("global", "region"), production = NULL)

Arguments

cells

A tibble with area_code, item_prod_code, production_t (production in the units of get_primary_production()'s "tonnes" rows), rainfed_ha, irrigated_ha and ratio_unbounded (as build_regime_yield_ratio() returns it). Other columns are kept.

bound

Which pool of national yields sets Y_max and Y_min: "global" (default, all countries) or "region" (the countries of the cell's WHEP region, the region column of regions_full; where the region has no yields for the item, the world's pool, stamped _global).

production

Optional get_primary_production() output (year, area_code, item_prod_code, unit, value) used instead of building it.

Value

cells with:

  • ratio: the irrigated:rainfed yield ratio used, after the bounds (1 on a trivial split).

  • yield_rainfed, yield_irrigated: production per hectare of each regime.

  • yield_max, yield_min: the bounds applied; NA where the item has no yields to set them.

  • method_regime_split: "yield_ratio", "trivial_rainfed_only", "trivial_irrigated_only", "no_area" or "no_ratio".

  • method_regime_bound: the ceiling: "not_binding", "clipped", "clipped_at_one" (lowered to 1 and still above Y_max: the mean yield itself exceeds it), "no_bound", "not_applicable_trivial" or "not_applicable" (no area, or no ratio).

  • method_rainfed_floor: the floor: "not_binding", "rainfed_floor", "rainfed_floor_at_one" (lowered to 1 and still below Y_min: the mean yield itself is below it), "no_bound", "not_applicable_trivial" or "not_applicable".

  • method_bound_source: which yields set the bounds: "own_yields", "bound_via_spam_crop", either suffixed "_global" where a regional pool fell back to the world's, or "none".

  • method_yield_bound: the bound chosen.

Examples

cells <- tibble::tribble(
  ~area_code, ~item_prod_code, ~production_t, ~rainfed_ha, ~irrigated_ha,
  ~ratio_unbounded,
  203L, 15L, 500, 100, 50, 1.8
)
production <- tibble::tribble(
  ~year, ~area_code, ~item_prod_code, ~unit, ~value,
  2010L, 203L, 15L, "tonnes", 3000,
  2010L, 203L, 15L, "ha", 1000
)
split_regime_yield(cells, production = production)
#> # A tibble: 1 × 16
#>   area_code item_prod_code production_t rainfed_ha irrigated_ha ratio_unbounded
#>       <int>          <int>        <dbl>      <dbl>        <dbl>           <dbl>
#> 1       203             15          500        100           50             1.8
#> # ℹ 10 more variables: ratio <dbl>, yield_rainfed <dbl>, yield_irrigated <dbl>,
#> #   yield_max <dbl>, yield_min <dbl>, method_regime_split <chr>,
#> #   method_regime_bound <chr>, method_rainfed_floor <chr>,
#> #   method_bound_source <chr>, method_yield_bound <chr>