Re: [R] R-users

From: Peter Dalgaard <P.Dalgaard_at_biostat.ku.dk>
Date: Tue, 18 Dec 2007 09:57:53 +0100

Kunio takezawa wrote:
> R-users
> E-mail: r-help_at_r-project.org
>
> I have a quenstion on "gam()" in "gam" package.
> The help of gam() says:
> 'gam' uses the _backfitting
> algorithm_ to combine different smoothing or fitting methods.
>
> On the other hand, lm.wfit(), which is a routine of gam.fit() contains:
>
> z <- .Fortran("dqrls", qr = x * wts, n = n, p = p, y = y *
> wts, ny = ny, tol = as.double(tol), coefficients = mat.or.vec(p,
> ny), residuals = y, effects = mat.or.vec(n, ny), rank = integer(1),
> pivot = 1:p, qraux = double(p), work = double(2 * p),
> PACKAGE = "base")
> It may indicate that QR decomposition is used to derive an additive model
> instead of backfitting.
> I am wondering if my guess is correct, or this "the _backfitting
> algorithm"
> has another meaning.
>
Please don't ask the same question multiple times!

And no, backfitting and QR are unrelated concepts. You need to read up on the theory, there are two fundamental books: Hastie & Tibshirani (gam package) and Simon Wood (mgcv package). Both are a bit much to ask to have summarized in email.

-- 
   O__  ---- Peter Dalgaard             Ă˜ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard_at_biostat.ku.dk)                  FAX: (+45) 35327907

______________________________________________
R-help_at_r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Received on Tue 18 Dec 2007 - 09:03:39 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Tue 18 Dec 2007 - 09:30:20 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.