I wrote an R-news note about this sort of thing in 2006, you can
navigate there via CRAN...

url:    www.econ.uiuc.edu/~roger            Roger Koenker
email    [EMAIL PROTECTED]            Department of Economics
vox:     217-333-4558                University of Illinois
fax:       217-244-6678                Champaign, IL 61820


On Jun 13, 2008, at 4:54 AM, Jan Graffelman wrote:

Hi,

I wish to write a new link function for a GLM. R's glm routine does
not supply the "loglog" link. I modified the make.link function adding
the code:

   }, loglog = {
       linkfun <- function(mu) -log(-log(mu))
       linkinv <- function(eta) exp(-exp(-eta))
       mu.eta <- function(eta) exp(-exp(-eta)-eta)
       valideta <- function(eta) all(eta != 0)
   }, stop(sQuote(link), " link not recognised"))
structure(list(linkfun = linkfun, linkinv = linkinv, mu.eta = mu.eta,
       valideta = valideta, name = link), class = "link-glm")
}


and then call glm with argument

glm(y~x1+x2+x3,family=binomial(link=make.link("loglog")),data=X)

and that seems to work.

Is this the way to include a new link function? Any other suggestions?

Jan.

--
------------------------------------------------------------------------
|Jan Graffelman |tel: +34-93-4011739 | |Dpt. of Statistics & Operations Research|fax: +34-93-4016575 | |Universitat Politecnica de Catalunya |email: [EMAIL PROTECTED] | |Av. Diagonal 647, 6th floor | www: | |08028 Barcelona, Spain | http://www-eio.upc.es/~jan/ |

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