compiletime load "module_ppp.so";
PPP obj = {};

obj.read("density.pos",  "n");
obj.read("velocity.pos", "v");
obj.xy_plane(0, 10, "nearest_neighbour");

obj.write_pos_scalar_binary("flux-Z-2D.pos", "Vertical flux [1/m^2 s]", n*v_z);
obj.write_pos_scalar_binary("density-relative.pos", "Relative density [1/m^2 s]", 
                            100*n/n_max);