Re: [R] "gam()" in "gam" package

From: Kunio takezawa <>
Date: Wed, 19 Dec 2007 10:10:44 +0900


> This iteration seems to be for "iteratively reweighted least squares" not
>for backfitting. And lm.wfit may solve multiple linear equation using
>QR decomposition; but I am not sure.

   Let me tell you something about my guess above. The iteration below is from 1 to maxit.

  for (iter in 1:maxit) {

        fit <- eval(


The help of "gam.control()" says:

   maxit: maximum number of local scoring iterations    bf.maxit: maximum number of backfitting iterations

Therefore the iteration above is local scoring iteration not backfitting iteration.

   The first line of "lm.wfit()" is:
function (x, y, w, offset = NULL, method = "qr", tol = 1e-07,  singular.ok = TRUE, ...)
There is no "bf.maxit" or its equivalent in these arguments. And it contains 'method = "qr"'; it may mean that this routine solves a multiple linear equation using QR decomposition.

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Received on Wed 19 Dec 2007 - 01:14:10 GMT

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