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]] > > ______________________________________________ > [email protected] 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 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
