

Hi R people

I am using regsubsets() to fit large numbers of models and collect summary statistics in order to perform a Bayesian analysis of multi-way ANOVA with specific prior information. In general the variables have differing numbers of levels >=2.  This works well but with variable of more than 2 levels there are naturally some arbitrary decisions about which treatment contrasts to include in the model matrix.  It's obviously easy to choose the 'standard' contrasts using 

options( contrasts = c( "contr.sum", "contr.poly" ))

with contr.helmert, contr.sum or contr.treatment as required.

However, what I would really like is a set of all pairwise comparison contrasts, and preferably in a form that can be fed straight to regsubsets() so that all labelling, fitting, output etc is automatically dealt with.

Are there any functions or libraries in R that will allow me to do this without too much grief?

Thanks in advance


Michael Hopkins
Algorithm and Statistical Modelling Expert
 
Upstream
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