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Subject: Re: [office-comment] Re: improvements for interpolation in charts

Hi Patrick,

On Thu, 2011-11-10 at 16:54 -0700, Patrick Durusau wrote:
> Will you have time to review the proposal Regina references in the 
> message with subject line: "polynomial regression curve in charts"?

The proposal referenced is quite incomplete and refers to an earlier
version of ODF than 1.2. It would be easy to adjust the proposal to ODF
1.2 but it is missing the specific calculation details. For example in
polynomial regression it needs to be more specifically stated in which
sense the "best" fit should be obtained. There are various ways this
could be defined leading to different regression curves. I don't think
we should include this in the standard unless we can be precise about
which regression curve is intended.

Since Gnumeric implements versions of this, I am obviously interested in
having it included in ODF (preferably ODF 1.3), but since this is not
just a question of reviewing the proposal I can't guarantee that I will
have sufficient time.


> Thanks!
> Hope you are having a great week!
> Patrick
> On 11/10/2011 03:29 PM, Andreas J. Guelzow wrote:
> > Hi Regina,
> >
> > On Thu, 2011-11-10 at 12:32 -0700, Regina Henschel wrote:
> >> 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.
> > In fact they should be relatively easy to implement. I'll put them on
> > the list of interpolation methods to define (hopefully for 1.3).
> >> 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.]
> > I really don't yet what specifically these methods are. I still have to
> > analyse the goffice code to see what they are calculating, determine
> > whether these are mathematically reasonable (and standard (in the sense
> > of "accepted in the field") and then write them down in a way that
> > non-mathematicians can implement them. I'll let you know when I have a
> > first draft.
> >
> > Andreas
> -- 
> Patrick Durusau
> patrick@durusau.net
> Chair, V1 - US TAG to JTC 1/SC 34
> Convener, JTC 1/SC 34/WG 3 (Topic Maps)
> Editor, OpenDocument Format TC (OASIS), Project Editor ISO/IEC 26300
> Co-Editor, ISO/IEC 13250-1, 13250-5 (Topic Maps)
> Another Word For It (blog): http://tm.durusau.net
> Homepage: http://www.durusau.net
> Twitter: patrickDurusau

Andreas J. Guelzow, PhD, FTICA
Concordia University College of Alberta

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