From: Michael <comtech.usa_at_gmail.com>

Date: Tue 28 Feb 2006 - 07:58:06 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Feb 28 08:17:06 2006

Date: Tue 28 Feb 2006 - 07:58:06 EST

Have you seen an example on how to do it in R? I found no practical examples...

On 2/27/06, vito muggeo <vmuggeo@dssm.unipa.it> wrote:

*>
*

> Dear Micheal,

*>
**> > the output of the "ns" function in R is "basis matrix", but then
**> Yes you are right, the output of the ns(x, df) is the basis matrix of a
**> natural cubic spline with df degrees of freedom. See ?ns (in package
**> splines) on how to specify df or knots or ..
**>
**> Fitting y~ns(x,df) yields a smooth curve given by a linear combination
**> of the basis functions (the single colums of the basis matrix) by the
**> estimated coefficients (returned by the fitted model).
**>
**> As far as I know, a tensor product is usually employed to
**> multidimensional smoothing and the multidimensional basis is formed via
**> the kronecker product of the marginal bases.
**>
**> Finally, last but not least: Probably you need some statistical
**> backaground on spline fitting..
**> Please, read some statistical papers/books on such topic (for instance
**> see references in packages splines, mgcv)
**>
**> best,
**> vito
**>
**> Michael wrote:
**> > Hi all,
**> >
**> > Could anybody recommend some easy-to-understand and example based
**> > notes/tutorials on how to use cubic splines to do filtering on
**> > multi-dimension data?
**> >
**> > I am confused by the 1-dimensional case, and more confused by
**> > multi-dimensional case.
**> >
**> > I found all the books suddenly become very abstract when it comes to
**> this
**> > subject.
**> >
**> > They don't provide examples in R or Splus at all.
**> >
**> > Specifically, I don't know how to provide data "x" to the "ns" function
**> in
**> > R,
**> >
**> > and I don't understand what should be the output matrix, and how to use
**> the
**> > output matrix to "filter" data?
**> >
**> > Books mention about basis matrix, design matrix, model matrix, data
**> matrix,
**> > etc. I got lost.
**> >
**> > I presume the output of the "ns" function in R is "basis matrix", but
**> then
**> > how do I use it? How to form tensor-product?
**> >
**> > I don't understand it at all.
**> >
**> > Please help me!
**> >
**> > Thank you very much!
**> >
**> > [[alternative HTML version deleted]]
**> >
**> > ______________________________________________
**> > R-help@stat.math.ethz.ch mailing list
**> > https://stat.ethz.ch/mailman/listinfo/r-help
**> > PLEASE do read the posting guide!
**> **http://www.R-project.org/posting-guide.html
**> >
**>
**> --
**> ====================================
**> Vito M.R. Muggeo
**> Dip.to Sc Statist e Matem `Vianelli'
**> Università di Palermo
**> viale delle Scienze, edificio 13
**> 90128 Palermo - ITALY
**> tel: 091 6626240
**> fax: 091 485726/485612
**> ====================================
**>
*

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Feb 28 08:17:06 2006

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