Generate an inner boundary polygon by shrinking an existing boundary inward

Computes an inward-shifted (contracted) boundary by applying a negative spatial buffer to an existing boundary polygon. This function is a wrapper around getOuterBoundary() and is useful for defining an inner region around a spatial cluster or structure.

Usage

getInnerBoundary(boundary = NULL, dist = 50)

Arguments

boundary

A data frame of boundary points (with columns x, y, region_id) or an sf object of POLYGON geometries.

dist

A positive numeric value specifying how far inward to shrink the boundary. This is automatically converted to a negative buffer distance. Default is 50.

Value

An sf object containing the inward-shrunk polygons, one per region_id.

Details

Be careful: if the shrinkage distance is too large, the resulting geometry may become invalid or disappear entirely, especially for narrow or irregular shapes.

See also

getOuterBoundary() for the outward (positive) buffer version.

Examples

# Load coordinates
coords <- readRDS(system.file("extdata", "MouseBrainCoords.rds",
    package = "SpNeigh"
))

# Get boundary polygons of cluster 2
boundary_points <- getBoundary(data = coords, one_cluster = 2)
boundary_polys <- buildBoundaryPoly(boundary_points)
plot(boundary_polys)


# Generate inner boundary with 50-unit buffer for boundary region 1
inner_boundary <- getInnerBoundary(boundary_polys)
#> Warning: Some inner boundaries may have collapsed or disappeared due to excessive shrinkage.
plot(inner_boundary)