int closept[] = pcfind(0, "Cd", @Cd, 0.1, 9);
vector kernelsum = 0;
vector firstcol = point(0, "Cd", closept[0]);

for (int i = 1; i < 9; i++){
    vector closecol = point(0, "Cd", closept[i]);
    kernelsum += ( closecol * -1 );
}
f@density = length( kernelsum += ( firstcol * 8 ) );