A very fast 2D concave hull algorithm — concaveman • concaveman

The concaveman function ports the concaveman library from mapbox. It computes the concave polygon for one set of points.

Usage

concaveman(points, concavity, length_threshold)

# S3 method for class 'matrix'
concaveman(points, concavity = 2, length_threshold = 0)

# S3 method for class 'sf'
concaveman(points, concavity = 2, length_threshold = 0)

# S3 method for class 'sfc'
concaveman(points, concavity = 2, length_threshold = 0)

Arguments

points: the points for which the concave hull must be computed. Can be represented as a matrix of coordinates or an sf object.
concavity: a relative measure of concavity. 1 results in a relatively detailed shape, Infinity results in a convex hull. You can use values lower than 1, but they can produce pretty crazy shapes.
length_threshold: when a segment length is under this threshold, it stops being considered for further detalization. Higher values result in simpler shapes.

Value

an object of the same class as points: a matrix of coordinates or an sf object.

Details

For details regarding the implementation, please see the original javascript library github page. This is just a thin wrapper, via V8.

Examples

data(points)
polygons <- concaveman(points)
plot(points)
plot(polygons, add = TRUE)