From: Michael <comtech.usa_at_gmail.com>

Date: Tue 28 Feb 2006 - 09:31:23 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 09:41:19 2006

Date: Tue 28 Feb 2006 - 09:31:23 EST

I think you mis-understood. And perhaps you read in a haste, or you were just in a bad mood today.

I think on this mailing-list, many people come for help on a R related issue, they know something theoretically, but since they are new to R, they want to use R, they want to use R to help do applied things.

For me, there is a missing link between my understanding of splines from the books(which are abstract) and a usage example in R. That's something I am looking for. I believe it is very appropriate.

If you don't know, or don't want to say anything helpful, please just don't say anything. It is not about a gun pointing, it is about a learning process which is very specific to R.

Please kindly try not to say negative things, and try to discourage people from learning new things.

On 2/27/06, Liaw, Andy <andy_liaw@merck.com> wrote:

*>
*

> If you do not understand what ns() outputs, nor descriptions of splines in

*> books, perhaps it's not an appropriate tool for you. Look for something
**> that you understand (or can understand after some reading). No one is
**> pointing a gun to your head and tell you to use splines, I hope.
**>
**> If you have a hard time understanding what you read in books, it's
**> unrealistic to expect a mailing list about a software to teach you.
**>
**> Andy
**>
**> From: Michael
**> >
**> > 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]]
**> >
**> >
**>
**>
**>
**> ------------------------------------------------------------------------------
**> Notice: This e-mail message, together with any attachment...{{dropped}}
*

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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 09:41:19 2006

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