raster_edge_length: Calculate the total edge length of a raster associated with...
In ecological-cities/home2park: Spatial Provision of Urban Parks

View source: R/parks_calc_attributes_helpers.R

raster_edge_length

R Documentation

Calculate the total edge length of a raster associated with each park polygon

Description

Helper function within parks_calc_attributes(). The total edge length of (classified) raster patches contained within the polygons will be calculated. Additionally, the argument raster_edge_buffer provides a way include patches in close proximity to the polygons. The total edge lengths are summed together and appended to the polygons data as additional columns (or one column, if there is only one raster class). Note that this operation may take a while to complete, as it involves the conversion of rasters to polygons (and vice versa).

Usage

raster_edge_length(
  polygons,
  raster,
  raster_min_patch_size = units::set_units(0, "m^2"),
  raster_edge_buffer = units::set_units(0, "m^2"),
  relative = TRUE
)

Arguments

`polygons`	`sf` (with projected coordinate reference system).
`raster`	`SpatRaster` object from `terra::rast()`. Should have a (projected) coordinate reference system similar to `polygons`.
`raster_min_patch_size`	Minimum patch size to be included in results. Provided either as a units object (see `units::set_units()`), or a number in the units of the coordinate reference system. Defaults to `0` m^2.
`raster_edge_buffer`	numeric. Specify buffer distance to add to polygonised raster; the total edge length of `polygons` that intersect the buffered `raster` will be summed up together with the total edge length contained within the `polygons`. Defaults to `0` (only patches fully contained within polygons will be considered). Provided either as a units object (see `units::set_units()`), or a number in the units of the coordinate reference system.
`relative`	logical. Whether or not to calculate relative amounts (i.e. ratio of edge-to-perimeter length). Defaults to `TRUE`.

Value

polygons with added column(s) ⁠< class value >_length⁠, and ⁠< class value >_length_perim_ratio⁠ if relative is set to TRUE. Note that the value 0 will be summarised; convert pixels to NA if you wish to exclude them.