[R] tan(mu) link in GLM

Prof Brian Ripley ripley at stats.ox.ac.uk
Fri Apr 2 16:22:45 CEST 2004

On Fri, 2 Apr 2004 Ted.Harding at nessie.mcc.ac.uk wrote:

> I am interested in extending the repertoire of link functions
> in glm(Y~X, family=binomial(link=...)) to include a "tan" link:
>    eta = (4/pi)*tan(mu)
> i.e. this link bears the same relation to the Cauchy distribution
> as the probit link bears to the Gaussian. I'm interested in sage
> advice about this from people who know their way aroung glm.
> From the surface, it looks as though it might just be a matter
> of re-writing 'make.link' in the obvious sort of way so as to
> incorporate "tan", but I fear traps ...

How are you going to do that?  If you edit make.link and have your own 
local copy, the namespace scoping will ensure that the system copy gets 
used, and the code in binomial() will ensure that even that does not get 
called except for the pre-coded list of links.

> What am I missing?

You need a local, modified, copy of binomial, too, AFAICS.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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