[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
expected).
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,
Rob
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