libpysal.cg.voronoi_frames

libpysal.cg.voronoi_frames(points, radius=None, clip='extent')[source]

Composite helper to return Voronoi regions and generator points as individual dataframes.

Parameters
pointsarray_like

The originator points.

radiusfloat

The distance to “points at infinity” used in building voronoi cells.

clipstr, shapely.geometry.Polygon

An overloaded option about how to clip the voronoi cells. The options are:

  • ‘none’/None: No clip is applied. Voronoi cells may be arbitrarily larger that the source map. Note that this may lead to cells that are many orders of magnitude larger in extent than the original map. Not recommended.

  • ‘bbox’/’extent’/’bounding box’: Clip the voronoi cells to the bounding box of the input points.

  • ‘chull’/’convex hull’: Clip the voronoi cells to the convex hull of the input points.

  • ‘ashape’/’ahull’: Clip the voronoi cells to the tightest hull that contains all points (e.g. the smallest alphashape, using libpysal.cg.alpha_shape_auto).

  • Polygon: Clip to an arbitrary Polygon.

tolerancefloat

The percent of map width to use to buffer the extent of the map, if clipping (default: .01, or 1 percent).

Returns
reg_vtxtuple

Two geopandas.GeoDataFrame (or pandas.DataFrame if geopandas is unavailable) objects–(region_df, points_df)–of finite Voronoi polygons and the originator points as geometries.

Notes

If geopandas is not available the return types will be pandas.DataFrame objects, each with a geometry column populated with PySAL shapes. If geopandas is available, return types are pandas.GeoDataFrame objects with a geometry column populated with shapely geometry types.

Examples

>>> points = [(10.2, 5.1), (4.7, 2.2), (5.3, 5.7), (2.7, 5.3)]
>>> regions_df, points_df = voronoi_frames(points)
>>> regions_df.shape
(4, 1)
>>> regions_df.shape == points_df.shape
True