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Compute overlap allocation ratios between polygons

get_overlap_allocation.Rd

Calculates the proportion of each fine-grain polygon (from_geom) overlapping with coarse-grain polygons (to_geom), returning allocation ratios for crosswalking data. Use to allocate values between geographies based on area overlap.

Usage

get_overlap_allocation(
  overlap_sf,
  from_geom,
  to_geom,
  from_key,
  to_key,
  method = "area",
  overlap_tol,
  preserve_representatives = FALSE
)

Arguments

overlap_sf

sf object. Subset of from_geom polygons to allocate.

from_geom

sf object. Fine-grain geometry to convert from.

to_geom

sf object. Coarse-grain geometry to convert to.

from_key

character vector. Key columns for from_geom.

to_key

character vector. Key columns for to_geom.

method

character(1). Allocation method. Only 'area' supported. Default 'area'.

overlap_tol

numeric(1). Cutoff for accepted overlaps (e.g., 0.05).

preserve_representatives

logical(1). If TRUE, keeps at least one representative per from_geom. Default FALSE.

Value

data.table. Overlap allocation ratios with keys and overlap_ratio. Columns:

  • from_key <character/integer> — key for fine-grain geometry

  • to_key <character/integer> — key for coarse-grain geometry

  • overlap_ratio — proportion of from_geom area overlapping to_geom Rows: one per overlap pair. Keys: (from_key, to_key).

Details

  • Transforms input geometries to equal area projection for accurate area calculation.

  • Computes intersection polygons and their areas.

  • Calculates overlap ratio for each from_geom as intersection area divided by from_geom area.

  • Removes slivers and adjusts overlap ratios based on provided tolerance.

  • If preserve_representatives is TRUE, ensures at least one representative per from_geom.

  • Returns a data.table with keys and overlap_ratio; does not modify by reference.

  • Assumes valid sf geometries and keys; errors if empty or invalid.

Settings

None.

See also

get_xwalk_sfx_to_sfy

Other ACS utilities: get_acs_bg_counts(), get_acs_bg_counts_base(), get_puma_ids(), get_pumas(), get_tracts_puma_xwalk(), get_xwalk_sfx_to_sfy(), load_xwalk()

Examples

## Not run:
get_overlap_allocation(overlap_sf, from_geom, to_geom, from_key, to_key)
#> Error in get_overlap_allocation(overlap_sf, from_geom, to_geom, from_key,     to_key): could not find function "get_overlap_allocation"
## End(Not run)