improvements for interpolation in charts

[Regina Henschel <rb.henschel@t-online.de>]

Hi all,

I have noticed, that you are discussing improvements for interpolations 
in charts. Currently both kind of interpolations are parametric. That 
gives nice curves, but for some functions the result can be better with 
non-parametric methods. So I want to see non-parametric interpolation 
methods in addition. For example my textbook "Engeln-Müllges, Gisela: 
Numerik-Algorithmen" suggests the "Akima Subsplines" for not smooth 
functions. It should be possible to use such interpolations too.

If the already made suggestion "fixed derivatives at both ends" includes 
"non-parametric" too, I would second that kind.

I do not find the term "parabolic limits" besides in the description of 
the application "goffice". What does it mean? Is it the same as 
"parabolically terminated"? And what does "cubic limits" mean?
[I'm no professional mathematician, but will implement those 
interpolations. So please excuse me, if my questions are stupid.]

Kind regards
Regina