GeometricMedian Class Reference

Inheritance diagram for GeometricMedian:

Collaboration diagram for GeometricMedian:

Public Member Functions
String	getURI ()
Coordinate	getGeoMedian (Coordinate start, Coordinate[] points)
Value	evaluate (ValueFactory valueFactory, Value... args) throws ValueExprEvaluationException

Protected Member Functions
Geometry	operation (Geometry geom)

Static Private Member Functions
static double	distance (double x1, double y1, double x2, double y2)

Member Function Documentation

distance()

static double distance ( double  x1, double  y1, double  x2, double  y2  )

staticprivate

Referenced by GeometricMedian.getGeoMedian().

                                                                           {
    x1 -= x2;
    y1 -= y2;
    return Math.sqrt(x1 * x1 + y1 * y1);
}

evaluate()

Value evaluate ( ValueFactory  valueFactory, Value...  args  ) throws ValueExprEvaluationException

inherited

References LiteralRegistry.getLiteral(), and GeometricUnaryFunction.operation().

                                                                                                            {
                if (args.length != 2) {
                        throw new ValueExprEvaluationException(getURI() + " requires exactly 2 arguments, got " + args.length);
                }
                
                LiteralType l=LiteralRegistry.getLiteral(((Literal)args[0]).getDatatype().toString());
                if(l instanceof VectorLiteral) {
                        Geometry geom=((VectorLiteral)l).read(args[0].stringValue());
                        Geometry result = operation(geom);
                        return valueFactory.createLiteral(((VectorLiteral) l).unparse(result),((Literal)args[0]).getDatatype());
                }
                throw new ValueExprEvaluationException("Argument given is not a geometry literal");
        }

getGeoMedian()

Coordinate getGeoMedian	(	Coordinate	start,
		Coordinate []	points
	)

References GeometricMedian.distance(), Coordinate.x, and Coordinate.y.

Referenced by GeometricMedian.operation().

                                                                     {
    double cx = 0;
    double cy = 0;

    double centroidx = start.x;
    double centroidy = start.y;
    do {
        double totalWeight = 0;
        for (int i = 0; i < points.length; i++) {
            Coordinate pt = points[i];
            double weight = 1 / distance(pt.x, pt.y, centroidx, centroidy);
            cx += pt.x * weight;
            cy += pt.y * weight;
            totalWeight += weight;
        }
        cx /= totalWeight;
        cy /= totalWeight;
    } while (Math.abs(cx - centroidx) > 0.5
            || Math.abs(cy - centroidy) > 0.5);// Probably this condition
                                                // needs to change

    return new Coordinate(cx, cy);
}

getURI()

String getURI

(

)

References POSTGIS.st_geometricMedian.

                               {
                return POSTGIS.st_geometricMedian.stringValue();
        }

operation()

Geometry operation ( Geometry  geom )

protected

References GeometricMedian.getGeoMedian().

                                                    {
            Coordinate median=getGeoMedian(geom.getCentroid().getCoordinate(), geom.getCoordinates());
            GeometryFactory fac=new GeometryFactory();
            return fac.createPoint(median);
        }