From the EGRET package http://usgs-r.github.io/EGRET/ Robert Hirsch and
Laura De Cicco
Usage
triCube(d, h)
Arguments
d
numeric vector of distances from the point of estimation to the
given sample value
h
numeric value, the half-window width, measured in the same units as
d
Value
w numeric vector of weights, all 0<=w<=1
Details
Computes the tricube weight function on a vector of distance values (d),
based on a half-window width of h, and returns a vector of weights that
range from zero to 1.