From: "Sanne Christensen" <sc_trold@hotmail.com>
Path: news.mathworks.com!newsfeed-00.mathworks.com!webx
Newsgroups: comp.soft-sys.matlab
Subject: Re: Curve fitting a 3D data set
Message-ID: <eef3579.7@webx.raydaftYaTP>
Date: Wed, 24 Nov 2004 15:47:46 -0500
References: <eef3579.-1@webx.raydaftYaTP> <cnjb5n$guv$1@news-int2.gatech.edu> <eef3579.2@webx.raydaftYaTP> <cnl2d2$cd5$1@fb04373.mathematik.tu-darmstadt.de>
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Yes - I do mean a curve (when my programme is done it has to
represent a rib of a pig) :) I have looked at the lsqcurvefit, but it
seems that it also only utilises 2D data sets? (or have I missed
something? ;o))

/Sanne

Peter Spellucci wrote:
>
>
>
> In article <eef3579.2@webx.raydaftYaTP>,
> Sanne <sc_trold@hotmail.com> writes:
> >That is exactly what I am trying to do. My data should fit to
> >something like a poly of second order (parabola) and I could
only
> >find functions (polyfit) which could do it in 2D
> >
> >Teddy Hsung wrote:
> >>
> >>
> >> My understanding to you question is that you have a known
form
> of
> >> function
> >> with some unknown parameters. And you have bunch of 3D
data.
> You
> >> want to fit
> >> those data to get the parameters??
> >>
> >> If so, the optimization toolbox can help you out. If you
can
> >> provide more
> >> details, I would be happy to give it a try.
> >>
> >> Rentian
> >>
> >> "Sanne Christensen" <sc_trold@hotmail.com> wrote in
message
> >> news:eef3579.-1@webx.raydaftYaTP...
> >>> I'm pretty new in the Matlab-world. How do I make
curve
> fitting
> >> on a
> >>> 3D data set (x, y, z)? Do I need a special toolbox for
it?
> >>>
> >>> Thanx for your help :)
> >>> Sanne
> >>
> >>
> >>
>
> as long as only a polynomial model is to used, \ alone will do the
> job for you
> otherwise you will need lsqcurvefit from the optimization toolbox.
> but ... (x,y,z) -data: and "curvefitting" you mean indeed a curve?
> not a surface? and then: which model do you have for that curve?
> parametric : (a+b*t+c*t^2 ; d+e*t+f*t^2; g+h*t+i*t^2) with
> t the curve parameter (how to get this?) or implicit:
> (intersection of two surfaces)
> a(i)+b(i)*x+c(i)*y+d(i)*x^2+e(i)*x*y+f(i)*y^2=0 i=1,2
> plus some normalization constraints?
> hth
> peter
>
>
>
>