A query in BigQuery that leverages a Javascript library to compute a voronoi diagram.

bq_udf_voronoi.sql

#standardSQL
CREATE TEMP FUNCTION
  testVolonoi (data ARRAY<STRUCT<x float64, y float64, id string, name string>>, margin_ratio float64)
  RETURNS ARRAY<STRUCT<id string, name string, wkt String>>
  LANGUAGE js AS """
 
  let xl,xr=data[0].x;
  let yt,yb=data[0].y;
  for(i=1;i<data.length;i++){
    if(data[i].x < xl) xl=data[i].x ;
    if(data[i].x > xr) xr=data[i].x ;
    if(data[i].y < yt) yt=data[i].y ;
    if(data[i].y > yb) yb=data[i].y ;
  }
  box_width =xr-xl;
  box_height=yb-yt;
  
  
  bbox={
    xl: xl - box_width  * margin_ratio, 
    xr: xr + box_width  * margin_ratio, 
    yt: yt - box_height * margin_ratio, 
    yb: yb + box_height * margin_ratio
  };
 
  voronoi=new Voronoi();
  diagram = voronoi.compute(data, bbox);
  cells=diagram.cells;
  
  let results=new Array();
  for (var i=0;i<cells.length;i++){
    let halfedges=cells[i].halfedges;
    
    let wkt_polygon="POLYGON((";
    
    let vertex0=halfedges[0].getStartpoint();
    wkt_polygon+= vertex0.x +" "+vertex0.y;

    for (j=0;j<halfedges.length;j++){
      let vertex=halfedges[j].getEndpoint();
      wkt_polygon+=","+vertex.x+" "+vertex.y;
    }
    
    wkt_polygon+="))";
    
    results.push({"wkt":wkt_polygon, "id":data[i].id, "name":data[i].name});
  }
  
  return results;
  """
OPTIONS
  # loading hosted opensource library : https://github.com/gorhill/Javascript-Voronoi
  ( library="gs://moritani-bigdata-sgtaxi-us/udf/volonoi/rhill-voronoi-core.min.js" );
  #  ( library="gs://moritani-bigdata-sgtaxi-us/udf/volonoi/rhill-voronoi-core.js" );
SELECT
  id, name, wkt
FROM
  UNNEST(testVolonoi( ARRAY (
      SELECT
        STRUCT(
          location.longitude AS x,
          location.latitude  AS y,
          station_id         AS id,
          name) AS data
      FROM
        `moritani-bigdata.sg_taxi_prediction.rainfall_preproc`
      GROUP BY
        station_id, name, location.longitude, location.latitude ), 0.2))