doubt in book "antenna and EM modeling with matlab"

Hi
I have come doubt in the code given in the book"antenna and EM modeling with matlab" by sergey N.Makarov. Why they have introduce offset while plotting the radiation pattern. Please do reply
Thankyou

For every circuit in electronics with active elements there will be some offset voltage.
Matlab doesn't show offset voltage.
So they introduce offset while plotting the radiation pattern.