py_geo_voronoi

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infochimps Voronoi

Created by Hohyon Ryu, Aug/22/2011

• Dependencies

• shapely : sudo apt-get install python-shapely
• matplotlib (pylab) : sudo apt-get install python-matplotlib
• Built on Steve Fortune's Python Voronoi Code Steve Fortune's homepage: http://netlib.bell-labs.com/cm/cs/who/sjf/index.html

• Files

  README globalmaptiles.py - Google Geo-coordinate Library voronoi.py - Voronoi lattice library (line and vertices based) voronoi_poly.py - Voronoi lattice library (polygon based)

  sample_city_data.csv - sample data

  main_example.py - code example

• Inputs:

  1. Dictionary of the points: (You can use simple sequential number for the dictionary keys or some text to associate with.) PointsMap={} PointsMap["stationA"]=(-143.22, 38.22) PointsMap["stationB"]=(-122.22, 56.22) PointsMap[1]=(-122.22, 56.22)

  2. The bounding box (left_top_x, left_top_y, bottom_right_x, bottom_right,y) to generate a voronoi lattice. Bounding Box Options: You can either use the name or the coordinates "AUSTIN" [30.8, -98.5, 29.535, -97.031] "TX" [36.5, -106, 25, -93] "US" [55, -130, 23, -60] "GUS" [60, -140, 22, -50] "KR" [45, 120, 32, 135] (Korea) "W" [90, -180, -90, 180] (World, Default)

  3. PlotMap: shows the voronoi lattice on a map. This may be extremely slow if you have more than 1M points. (Default is False, Not available for VoronoiLineEdges)

• Output options:

  1. Stations, Lines and edges Example: import voronoi_poly vl=voronoi_poly.VoronoiLineEdges(PointsMap)

  Output: vertices, lines, edges, station_to_edge (1) a list of 2-tuples, which are the x,y coordinates of the Voronoi diagram vertices (2) a list of 3-tuples (a,b,c) which are the equations of the lines in the Voronoi diagram: ax + by = c (3) a list of 3-tuples, (l, v1, v2) representing edges of the Voronoi diagram. l is the index of the line, v1 and v2 are the indices of the vetices at the end of the edge. If v1 or v2 is -1, the line extends to infinity.
  (4) a dictionary, where keys are the station numbers(vertices), and the values are the number of edges surrounding the vertice.

  2. Polygons import voronoi_poly vl=voronoi_poly.VoronoiPolygons(PointsMap, BoundingBox="AUSTIN", PlotMap=False) Output: 185: {'coordinate': (3.04, 36.77), 'info': 'Algiers/Algeria', 'obj_polygon': <shapely.geometry.polygon.Polygon object at 0x3152190>}

     • You can access the polygon coordinates by the following example:

       from shapely.geometry import Polygon
       print list(polygon_data.exterior.coords)

  3. Quadkey-based Grids on Polygons import voronoi_poly

  vl=voronoi_poly.VoronoiPolygons(PointsMap, BoundingBox="W", PlotMap=False) voronoi_poly.GridVoronoi(vl, zl=7, PlotMap=True)
  Output: Quadkey, Station_name, Longitude, Latitude

  4. GeoJson Polygons import voronoi_poly voronoi_poly.VoronoiGeoJson_Polygons(PointsMap, BoundingBox="US") Output: Geojson Polygons

  5. GeoJson MultiPolygons import voronoi_poly voronoi_poly.VoronoiGeoJson_MultiPolygons(PointsMap, BoundingBox="KR") Output: Geojson MiltiPolygons