From: Liaw, Andy <andy_liaw_at_merck.com>

Date: Tue 28 Feb 2006 - 08:47:58 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 08:57:44 2006

Date: Tue 28 Feb 2006 - 08:47:58 EST

From: Michael

*>
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> 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
**> > ====================================
**> >
**>
**> [[alternative HTML version deleted]]
**>
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>

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 08:57:44 2006

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