Get point associated with Voronoi region (scipy.spatial.Voronoi)
I was misreading the docs. It says:
point_region: Index of the Voronoi region for each input point.
and I was using point_region
it as if it were the: "Index of the input point for each Voronoi region".
Instead of using:
points[i]
the correct point coordinates for each region can be obtained with:
np.where(vor.point_region == i)[0][0]
For your first question:
The issue is that there are N+1 regions (polygons) defined for the N points, and I'm not sure what this means.
This is because your vor.regions will always have an empty array. Something like
[[],[0, 0],[0, 1],[1, 1]]
This is related to your second question:
Another thing I don't understand is why are there empty vor.regions stored? According to the docs: regions: Indices of the Voronoi vertices forming each Voronoi region. -1 indicates vertex outside the Voronoi diagram. What does an empty region mean?
By default Voronoi() uses QHull with options 'Qbb Qc Qz Qx' enabled (qhull.org/html/qvoronoi.htm). This inserts a "point-at-infinity" which is used to improve precision on circular inputs. Therefore, being a "fake" point, it has no region. If you want to get rid of this, try removing the Qz option:
vor = Voronoi(points, qhull_options='Qbb Qc Qx')