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Dasymetric redistribution via a point layer

Source: R/redistribute_parcels.R
redistribute_parcels.Rd

Distributes each source value across the points (e.g. parcel centroids) that fall inside it, then reaggregates the point-level values to target polygons. With weights = NULL the value is split evenly across points; otherwise it is split in proportion to a points column (the extension point for household-size or unit-count weighting).

Usage

redistribute_parcels(
  source,
  target,
  points,
  extensive = NULL,
  weights = NULL,
  suffix = NULL
)

Arguments

source

An sf polygon layer carrying the values to redistribute.

target

An sf polygon layer to estimate values for.

points

An sf point layer (e.g. parcel centroids).

extensive

Character vector of count column names in source.

weights

Optional name of a numeric column in points to weight by.

suffix

Optional string appended to each new column name.

Value

The target layer (an sf object) with one new column per measure.

Details

Each source value is split across the points inside that source polygon in proportion to weights (equally when weights = NULL), then summed within each target polygon. A source polygon that contains no points contributes nothing to any target (its value cannot be placed). If the total weight of a source's points is zero, that source likewise contributes nothing. If target already has a column named like a redistributed measure, it is overwritten; pass suffix to keep both.

Examples

src <- sf::st_sf(pop = 100, geometry = sf::st_sfc(
  sf::st_polygon(list(rbind(c(0,0), c(2,0), c(2,2), c(0,2), c(0,0)))),
  crs = 3857))
tgt <- sf::st_sf(id = c("A", "B"), geometry = sf::st_sfc(
  sf::st_polygon(list(rbind(c(0,0), c(1,0), c(1,2), c(0,2), c(0,0)))),
  sf::st_polygon(list(rbind(c(1,0), c(2,0), c(2,2), c(1,2), c(1,0)))),
  crs = 3857))
pts <- sf::st_sf(geometry = sf::st_sfc(
  sf::st_point(c(0.5, 1)), sf::st_point(c(1.5, 1)), crs = 3857))
redistribute_parcels(src, tgt, pts, extensive = "pop")
#> Simple feature collection with 2 features and 2 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 0 ymin: 0 xmax: 2 ymax: 2
#> Projected CRS: WGS 84 / Pseudo-Mercator
#>   id                       geometry pop
#> 1  A POLYGON ((0 0, 1 0, 1 2, 0 ...  50
#> 2  B POLYGON ((1 0, 2 0, 2 2, 1 ...  50