How to avoid complex smoothing operators

"Shuman (1957) pointed out that any symmetrical centered smoothing operator could be expressed as a sequence of "smoothing elements" that he defined as symmetrical, centered three-point operators. For generality, however, smoothing elements must include those whose weights include complex numbers. For the large operator to be real, an element with a complex index, v, must be paired with one whose index is the complex conjugate of v. The index, v, he so defined that (l-v) is the weight of the central point"--Page 1. Frederick G. Shuman. "March 1976." System requirements: Adobe Acrobat Reader. 1976 NWS (National Weather Service) Library Public Domain 1931