[R] cubic spline/smoother with nlme

[Suzette Blanchard]

Greetings,  I would like to use a cubic spline
or smoother to model the fixed effects within
nlme.  So far the only smoother I have been able
to get to run successfully in nlme is smooth().

I tried smooth.spline:
   fixed=list(lKa~1,lCL~smooth.spline(BSA, df=3))
   the error I got was the following.
   Error in model.frame(formula, rownames, variables, varnames, extras,
   extranames,  :  invalid variable type

Can anyone suggest a cubic spline that would work within
this context?

Thank you for any help you can send,
Suzette


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Suzette Blanchard, Ph.D.
UCSD-PPRU