Re: [R] how to use the basis matrix of "ns" in R? really confused by multi-dim spline filtering?

From: Michael <comtech.usa_at_gmail.com>
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'
> UniversitÓ di Palermo
> viale delle Scienze, edificio 13
> 90128 Palermo - ITALY
> tel: 091 6626240
> fax: 091 485726/485612
> ====================================
>

        [[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 Received on Tue Feb 28 08:17:06 2006

This archive was generated by hypermail 2.1.8 : Tue 28 Feb 2006 - 09:08:49 EST