functions:smoothing:SPLSMOOTH

arc_length

 The normalized length of x is the real length divided by the range
 of x, that is, the maximum xin value minus the minimum value. The
 normalized length in y is the real length divided by the range of
 y. The arclength at a point is approximated by the sum of the
 lengths of straight line segments connecting all points up to that
 point.

WEIGHTS

 syntax:  SPLSMOOTH( x,y,n,w )

 If m is the length of w, x and y, the goal is to achieve:
 sum(i=1 to m) of ((G[i]-y[i])/w[i])^2 = s  where G[i] is the
 cubic spline function at x[i] and s is the spline tension.
 As w[i] decreases, the spline fits the data point (x[i],y[i])
 more closely.