Did You Know?
A binomial filter is a statistical smoothing technique that is used to reveal underlying trends in data. The nine points refer to the number of weighted terms used to approximate the Gaussian distribution (the more points, the closer the curve tends towards a normal, or "bell-shaped" distribution). In a 9-point binomial filter, four data values on each side of a given value are averaged with decreasing weights further from the center value to arrive at a smoothed value. This is a recognized method of data smoothing, common in climate analysis. Additional information can be obtained from Aubury, M. and Luk, W., Binomial filters, J. VLSI Signal Processing Volume 12, Number 1, (January 1996), 35-50.