!P.Nsum
Corresponding Plot Keyword: Nsum The number of adjacent points to sum to obtain a plotted point. If !P.Nsum is larger than 1, every group of !P.Nsum points is averaged to produce one plotted point. If there are m data points, then m / !P.Nsum points are displayed. On logarithmic axes a geometric average is performed.
It is convenient to use Nsum when there is an extremely large number of data points to plot because it plots fewer points, the graph is less cluttered, and it is quicker.