With this function you can retrieve the y component of the center of mass of an entire group of particles. The group value is that which was returned when you created the group of particles using the function physics_particle_group_end, and the function will return a value which is the combined value of the currently set flags.
|group||The particle group to get.|
yy = physics_particle_group_get_centre_y(group1);
The above code will get the x and y position for the center of mass of the particle group indexed in the variable "group1" and store them in variables.