Dear Ferrets, Im need to comput the integral from East to West, although I got confused with the instructions in the Ferret's manual, which says: Let integral = my_var[Y=lo:hi@IIN] Let reverse_integral = my_var[Y=lo:hi@DIN] - my_var[X=lo:hi@IIN] Is it realy "X" in the second part of the equation? Or the correct is Y at the IIN? Is this the same as do "reserse integral iqual minus integral"? Thanks, Domingos.