In reply to Wendy.

As I say in the article PROC LOGISTIC supports the EFFECT statement, so you can create the splines directly in the grammar of the procedure. For example:

data cars;
set sashelp.cars;
where Origin in ('Asia' 'USA') and
Type in ('SUV' 'Sedan' 'Sports');
keep Origin weight Type model;
run;

/* The EFFECT statement is supported by PROC LOGISTIC */
proc logistic data=cars;
effect spl = spline(weight / details naturalcubic basis=tpf(noint)
knotmethod=percentiles(5) );
class Type;
model Origin = spl Type; /* fit model by using spline effects */
effectplot; /* create fit plot of the predicted probabilities */
run;