[R] Baseline terms for lrm

Rob James rob at aetiologic.ca
Tue Jan 18 20:51:38 CET 2011

Dear R-help and Prof. Harrell:

My question concerns the baseline state for continuous variable in lrm() 
within the RMS package.

I have a model which can be reduced to:

lrm(FT ~ rcs(V1, c(0, 1,5))

The model makes perfect sense if the baseline state is where V1>=5 but 
the model makes no sense if the baseline category is 0 (which I had 
Can someone point me to a reference, or suggest a command/test, to get 
the model to fess up to the baseline state. The variable V1 and V1' are 
shown in the model output, but there is no clear association between 
these pseudo-variables and the ranges specified in the cut. Thus, it is 
seems possible to misidentify the baseline value for the term.

Many thanks,


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