alphashape package

Module contents

Top-level package for Alpha Shape Toolbox.

alphashape.alphashape(points: Union[List[Tuple[float]], numpy.ndarray], alpha: Union[None, float] = None)

Compute the alpha shape (concave hull) of a set of points. If the number of points in the input is three or less, the convex hull is returned to the user. For two points, the convex hull collapses to a LineString; for one point, a Point.

Parameters:

• points (list or shapely.geometry.MultiPoint or geopandas.GeoDataFrame) – an iterable container of points

• alpha (float) – alpha value

Returns:

shapely.geometry.Polygon or shapely.geometry.LineString or shapely.geometry.Point or geopandas.GeoDataFrame: the resulting geometry

alphashape.alphasimplices(points: Union[List[Tuple[float]], numpy.ndarray]) → Union[List[Tuple[float]], numpy.ndarray]

Returns an iterator of simplices and their circumradii of the given set of points.

Parameters:

points – An N`x`M array of points.

Yields:

A simplex, and its circumradius as a tuple.

alphashape.circumcenter(points: Union[List[Tuple[float]], numpy.ndarray]) → numpy.ndarray

Calculate the circumcenter of a set of points in barycentric coordinates.

Parameters:

points – An N`x`K array of points which define an (N-1) simplex in K dimensional space. N and K must satisfy 1 <= N <= K and K >= 1.

Returns:

The circumcenter of a set of points in barycentric coordinates.

alphashape.circumradius(points: Union[List[Tuple[float]], numpy.ndarray]) → float

Calculte the circumradius of a given set of points.

Parameters:

points – An N`x`K array of points which define an (N-1) simplex in K dimensional space. N and K must satisfy 1 <= N <= K and K >= 1.

Returns:

The circumradius of a given set of points.

alphashape.optimizealpha(points: Union[List[Tuple[float]], numpy.ndarray], max_iterations: int = 10000, lower: float = 0.0, upper: float = 1.7976931348623157e+308, silent: bool = False)

Solve for the alpha parameter.

Attempt to determine the alpha parameter that best wraps the given set of points in one polygon without dropping any points.

Note: If the solver fails to find a solution, a value of zero will be returned, which when used with the alphashape function will safely return a convex hull around the points.

Parameters:

• points – an iterable container of points

• max_iterations (int) – maximum number of iterations while finding the solution

• lower – lower limit for optimization

• upper – upper limit for optimization

• silent – silence warnings

Returns:

The optimized alpha parameter

Return type:

float