Voronoi Polygons for 2-D Point Sets

Author: Serge Rey (http://github.com/sjsrey)

Basic Usage

import os
import sys

sys.path.append(os.path.abspath(".."))

from libpysal.cg.voronoi import voronoi, voronoi_frames

points = [(10.2, 5.1), (4.7, 2.2), (5.3, 5.7), (2.7, 5.3)]

regions, vertices = voronoi(points)

/tmp/ipykernel_4300/2901581476.py:1: FutureWarning: The 'voronoi' function is considered private and will be removed in a future release.
  regions, vertices = voronoi(points)
/home/runner/micromamba/envs/test/lib/python3.14/site-packages/libpysal/cg/voronoi.py:67: FutureWarning: The 'voronoi_regions' function is considered private and will be removed in a future release.
  vor = voronoi_regions(Voronoi(points), radius=radius)

regions

[[1, 3, 2], [4, 5, 1, 0], [0, 1, 7, 6], [9, 0, 8]]

vertices

array([[  4.21783296,   4.08408578],
       [  7.51956025,   3.51807539],
       [  9.4642193 ,  19.3994576 ],
       [ 14.98210684, -10.63503022],
       [ -9.22691341,  -4.58994414],
       [ 14.98210684, -10.63503022],
       [  1.78491801,  19.89803294],
       [  9.4642193 ,  19.3994576 ],
       [  1.78491801,  19.89803294],
       [ -9.22691341,  -4.58994414]])

region_df, point_df = voronoi_frames(points)

/tmp/ipykernel_4300/2172163060.py:1: FutureWarning: The 'as_gdf' parameter currently defaults to True but will default to False in a future release. Set it explicitly to avoid this warning.
  region_df, point_df = voronoi_frames(points)
/tmp/ipykernel_4300/2172163060.py:1: FutureWarning: The 'return_input' parameter currently defaults to True but will default to False in a future release. Set it explicitly to avoid this warning.
  region_df, point_df = voronoi_frames(points)

%matplotlib inline
import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots()
region_df.plot(ax=ax, color="blue", edgecolor="black", alpha=0.3)
point_df.plot(ax=ax, color="red")

<Axes: >
../../_images/2727c3553e4e997c3b48fec138835a67da3443cbefdc6f65830b08a2fa787f3f.png

Larger Problem

n_points = 200
np.random.seed(12345)
points = np.random.random((n_points, 2)) * 10 + 10
results = voronoi(points)
mins = points.min(axis=0)
maxs = points.max(axis=0)

/tmp/ipykernel_4300/3060736572.py:4: FutureWarning: The 'voronoi' function is considered private and will be removed in a future release.
  results = voronoi(points)
/home/runner/micromamba/envs/test/lib/python3.14/site-packages/libpysal/cg/voronoi.py:67: FutureWarning: The 'voronoi_regions' function is considered private and will be removed in a future release.
  vor = voronoi_regions(Voronoi(points), radius=radius)

regions, vertices = voronoi(points)

/tmp/ipykernel_4300/2901581476.py:1: FutureWarning: The 'voronoi' function is considered private and will be removed in a future release.
  regions, vertices = voronoi(points)

regions_df, points_df = voronoi_frames(points)

/tmp/ipykernel_4300/980072883.py:1: FutureWarning: The 'as_gdf' parameter currently defaults to True but will default to False in a future release. Set it explicitly to avoid this warning.
  regions_df, points_df = voronoi_frames(points)
/tmp/ipykernel_4300/980072883.py:1: FutureWarning: The 'return_input' parameter currently defaults to True but will default to False in a future release. Set it explicitly to avoid this warning.
  regions_df, points_df = voronoi_frames(points)

fig, ax = plt.subplots()
points_df.plot(ax=ax, color="red")

<Axes: >
../../_images/626f675481cc265699200b98a04dc6487deac98fe5bcbdf45233c7326faf7b32.png 
fig, ax = plt.subplots()
regions_df.plot(ax=ax, color="blue", edgecolor="black", alpha=0.3)
points_df.plot(ax=ax, color="red")

<Axes: >
../../_images/d94834c6ff1ca0a6059a5f5e4513d795112c3261ab2e5630ecd744c9d1cead22.png

Trimming

points = np.array(points)
maxs = points.max(axis=0)
mins = points.min(axis=0)
xr = maxs[0] - mins[0]
yr = maxs[1] - mins[1]
buff = 0.05
r = max(yr, xr) * buff
minx = mins[0] - r
miny = mins[1] - r
maxx = maxs[0] + r
maxy = maxs[1] + r

fig, ax = plt.subplots()
regions_df.plot(ax=ax, edgecolor="black", facecolor="blue", alpha=0.2)
points_df.plot(ax=ax, color="red")
plt.xlim(minx, maxx)
plt.ylim(miny, maxy)
plt.title(f"buffer: {r}, n: {n_points}")
plt.show()
../../_images/436d1e3dd2e4276fb3577d90cf45478e9dc8f4428885916d3419d82372288f6b.png

Voronoi Weights

from libpysal.weights.contiguity import Voronoi as Vornoi_weights

w = Vornoi_weights(points)

/home/runner/micromamba/envs/test/lib/python3.14/site-packages/libpysal/weights/contiguity.py:659: FutureWarning: `use_index` defaults to False but will default to True in future. Set True/False directly to control this behavior and silence this warning
  return cls.from_dataframe(region_df, **kwargs)

w.n

200

w.pct_nonzero

2.685

w.histogram

[(np.int64(1), np.int64(1)),
 (np.int64(2), np.int64(6)),
 (np.int64(3), np.int64(17)),
 (np.int64(4), np.int64(34)),
 (np.int64(5), np.int64(41)),
 (np.int64(6), np.int64(63)),
 (np.int64(7), np.int64(24)),
 (np.int64(8), np.int64(7)),
 (np.int64(9), np.int64(5)),
 (np.int64(10), np.int64(1)),
 (np.int64(11), np.int64(0)),
 (np.int64(12), np.int64(1))]

idx = [i for i in range(w.n) if w.cardinalities[i] == 12]

points[idx]

array([[16.50851787, 13.12932895]])