15.43.2  Notes 

The spline fit is based on the spline fitter from FXB$CG from the Stanford
SPSS package.

The general fit was originally adapted from ACM Algorithm #433, by Hiroshi
Akima.

The  interpolation by n will not give the same results as joining the data
by n, since the joininig is done after  the  data  coordinates  have  been
transformed into text coordinates.