[R] binomial(link="inverse")

Lucke, Joseph F Joseph.F.Lucke at uth.tmc.edu
Thu Sep 11 00:01:51 CEST 2008

Isn't the binomial-log used to obtain risk ratios from the coefficients
rather than odds-ratios? 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Thomas Lumley
Sent: Wednesday, September 10, 2008 4:36 PM
To: Prof Brian Ripley
Cc: r-help at r-project.org; Ben Bolker
Subject: Re: [R] binomial(link="inverse")

On Wed, 10 Sep 2008, Prof Brian Ripley wrote:
> As to why the list of links known by name is as it is, that seems 
> history. in part the White Book history of S.  I've always thought it
an error that 'log'
> was a standard link for binomial, as the range does not match the 
> specification of probabilities (and S did not do so, MASS Table 7.1 ).

I think I added binomial("log"): log-binomial regression is quite
popular and useful in epidemiology (where effect sizes are small enough
that keeping away from the boundary may be less of a problem than
people's inability to understand odds ratios).

As a side note, in (some versions of) S, due to partial matching,
binomial("log") is valid -- it just does logistic regression.


Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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