SplineFit - Parametrization ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg31289] SplineFit - Parametrization ?*From*: Justus Heimann <Heimann at ism.tu-berlin.de>*Date*: Fri, 26 Oct 2001 04:28:44 -0400 (EDT)*Organization*: Technical University Berlin, Germany*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I got a question concerning the "SplineFit[DATA, Cubic]" function of the NumericalMath`SplineFit` Package. My problem is to fit a cubic spline to a set of numerical 2d data. E.g. using simply x,y-data like: DATA := Table[{1.*i^2, Random[Real, {-1., 1.}]}, {i, 10}]; splinefit := SplineFit[DATA, Cubic]; splinefit[u=f(x,y)][[1]] =! x ??? I found that SplineFit works much more accurate like e.g. the function Interpolation. That's why I switched from Interpolation to SplineFit. The problem is, that using SplineFit (in contrast to Interpolation), specfific data along the curve only can be identified by the curve parameter value. But actually I'm interested to explicitly get a curve value f(x) as function of x! Is this possible with SplineFit ? In case not, does anybody know how are the parameter values linked to the x, y values ? It seems that the parameter, say "u=f(x,y)", is running like U=[0,1,2,...,Length[DATA]-1] along the data points, somehow a uniform (integer) curve parametrization. But what happens with the parameter in between data points ? Thanks alot, Justus