Dear S-Plus users,
I have a problem runing a logistic regression using the Design library.
If I fit a lrm with more than two variables I obtain the following result:
(taking as an example the acath data.frame used in "An Introduction to S and
The Hmisc and Design Libraries")
fit<-lrm(sigdz ~ age.tertile * sex + choleste)
Problem in model.matrix.default(Terms.ns, X): No data for variable
"age.tertile"
or if I use the rcs fuction
fit<-lrm(sigdz~rcs(age,4) * (sex + rcs(choleste, 4)))
Problem in model.matrix.default(Terms.ns, X): No data for variable "rcs(age,
4)"
What could be happening?
Thanks,
jose
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