Outlying points and roughness estimates
Natgrid has facilities
for special treatment of points near function values where the
function values are
not consistent with neighboring values. For each input
point an outlier index is calculated if the point
is not on the convex
hull; for points on the convex hull, a roughness
index is calculated. Both of these indices are a
normalized measure of the consistency of an input function
value with its
neighbors. For details on how these indices are defined and
The effects of using the outlier and roughness indices are
primarily to attenuate the influence of gradient estimates
near points with high values for either of the two indices.
that in the neighborhood of such points, the interpolation
tends more toward natural neighbor linear interpolation.
This prevents oversmoothing in those areas, and
oversmoothing could result in incorrect deductions being
made from analysis of the resulting surface.
surrounding outlying points, that are produced by some curve fitting
techniques, are also minimized. See