lwmpoint_extract_points_4d()

POINT4D* lwmpoint_extract_points_4d	(	const LWMPOINT *	g,
		uint32_t *	npoints,
		int *	input_empty
	)

Definition at line 172 of file lwgeom_median.c.

{
        uint32_t i;
        uint32_t n = 0;
        POINT4D* points = lwalloc(g->ngeoms * sizeof(POINT4D));
        int has_m = lwgeom_has_m((LWGEOM*) g);
 
        for (i = 0; i < g->ngeoms; i++)
        {
                LWGEOM* subg = lwcollection_getsubgeom((LWCOLLECTION*) g, i);
                if (!lwgeom_is_empty(subg))
                {
                        *input_empty = LW_FALSE;
                        if (!getPoint4d_p(((LWPOINT*) subg)->point, 0, &points[n]))
                        {
                                lwerror("Geometric median: getPoint4d_p reported failure on point (POINT(%g %g %g %g), number %d of %d in input).", points[n].x, points[n].y, points[n].z, points[n].m, i, g->ngeoms);
                                lwfree(points);
                                return NULL;
                        }
                        if (has_m)
                        {
                                /* This limitation on non-negativity can be lifted
                                 * by replacing Weiszfeld algorithm with different one.
                                 * Possible option described in:
                                 *
                                 * Drezner, Zvi & O. Wesolowsky, George. (1991).
                                 * The Weber Problem On The Plane With Some Negative Weights.
                                 * INFOR. Information Systems and Operational Research.
                                 * 29. 10.1080/03155986.1991.11732158.
                                 */
                                if (points[n].m < 0)
                                {
                                        lwerror("Geometric median input contains points with negative weights (POINT(%g %g %g %g), number %d of %d in input). Implementation can't guarantee global minimum convergence.", points[n].x, points[n].y, points[n].z, points[n].m, i, g->ngeoms);
                                        lwfree(points);
                                        return NULL;
                                }
 
                                /* points with zero weight are not going to affect calculation, drop them early */
                                if (points[n].m > DBL_EPSILON) n++;
                        }
                        else
                        {
                                points[n].m = 1.0;
                                n++;
                        }
                }
        }
 
#if PARANOIA_LEVEL > 0
        /* check Z=0 for 2D inputs*/
        if (!lwgeom_has_z((LWGEOM*) g)) for (i = 0; i < n; i++) assert(points[i].z == 0);
#endif
 
        *npoints = n;
        return points;
}

References getPoint4d_p(), LW_FALSE, lwalloc(), lwcollection_getsubgeom(), lwerror(), lwfree(), lwgeom_has_m(), lwgeom_has_z(), lwgeom_is_empty(), POINT4D::m, LWMPOINT::ngeoms, LWCOLLECTION::ngeoms, pixval::x, and pixval::y.

Referenced by do_median_test(), and lwmpoint_median().

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