Hi Statalist,
I cannot figure out how to do this... the attached graph is exactly what we want, but not the linear fit line; we want the predicted probabilities instead of the lfit. Here is the syntax that I used to get the attached graph. The spline regression is what we want (before 2002 and after 2002), but not the linear fit line. Is there a way to make this graph BUT with the predicted probabilities line and splined?

(note: num_inadeq is a 0-6 count var and the IV of interest is ostomyyears (which is a surgery year) and that ranges from 1953 to 2017)

Syntax:
** Piecewise scatter plot with predicted probabilities
nbreg num_inadeq ostomyyears ib5.educ_revised white female AGE
predict inadeq
twoway (scatter inadeq OSTOMY_DATE_YR) (lfit inadeq OSTOMY_DATE_YR if ostomyyears <=2002) ///
(lfit inadeq OSTOMY_DATE_YR if ostomyyears >=2002)

Any suggestions?