[R] lsmeans

Frank E Harrell Jr f.harrell at vanderbilt.edu
Fri Sep 26 22:25:30 CEST 2008

Nutter, Benjamin wrote:
> I hope you'll forgive me for resurrecting this thread.  My question
> refers to John Fox's comments in the discussion of lsmeans from 
> https://stat.ethz.ch/pipermail/r-help/2008-June/164106.html
> John you said, "It wouldn't be hard, however, to do the computations
> yourself, using the coefficient vector for the fixed effects and a
> suitably constructed model-matrix to compute the effects; you could also
> get standard errors by using the covariance matrix for the fixed
> effects."
> I've been able to make use of all of that except for the 'suitably
> constructed model-matrix' part.  I've looked through some other threads
> on this topic, but am still a little in the dark as to what I'd need to
> do to construct a suitable matrix.
> I would like to use the least squares means to develop parameter
> estimates for a parametric ROC analysis, as described by Mithat Gonen's
> book (Analyzing Receiver Operating Characteristic Curves with SAS,
> 2007).  
> Any suggestions on references that would explain how to go about
> constructing the suitable model matrix?  
> Many Thanks
> Benjamin

As an aside, what advantages does modeling an ROC curve have over doing 
direct covariate modeling of the response variable as usual?

Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University

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