Dear r users

I have a question in coding continuous variables in logistic regression.

When "rcs" is used in transforming variables, sometime it gives implausible
associations with the outcome although the model x2 is high.

So what's your tips and tricks in coding continuous variables.

P.S. How to code variables as linear+square in the formula such as lrm.
lrm(y~x+sqrt(x)) can't work.

Many thanks.

Yao Zhu.

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