In the Hmisc package there is a new data class 'mChoice' for multiple
choice variables. There are format and as.numeric methods (the latter
creates a matrix of dummy variables). mChoice variables are not allowed
by model.frame. Is there a way to specify a conversion function that
model.frame will use automatically? I would use as.factor here.
model.frame does not seem to use as.data.frame.foo for individual variables.
Thanks
Frank
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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