Recursive simple clustering of 2d data based on distance.

function split(list: TPointArray; w,h: Int32): T2DPointArray;
var
  lo,hi: Int32;

  function extract_connections_of(p: TPoint): TPointArray;
  var i: Int32;
  begin
    for i:=hi downto lo+1 do
      // the distance parameter
      if (Abs(p.x-list[i].x) <= w) and (Abs(p.y-list[i].y) <= h) then
      begin
        Result += list[i];
        Swap(list[i], list[hi]); //move towards end
        Dec(hi);                 //and ever look at it again
      end;
  end;

  function recurse_connections(p: TPoint): TPointArray;
  var i: Int32;
  begin
    Result := extract_connections_of(p);
    for i:=0 to High(result) do
      Result += recurse_connections(result[i]); //extend
  end;
begin
  lo := 0;
  hi := High(list);
  while lo <= hi do
  begin
    Result += recurse_connections(list[lo]) + [list[lo]]; //append
    inc(lo);
  end;
end;