Spline terms in Proc Genmod

[Ishor]

Experts,

I am trying to conduct negative binomial distribution with a spline terms ( Outcome: count and predictor ( months); it is a time series analysis). Is there a way we can directly add spline in the model. 

I saw the following approach for Poisson distribution however negbin is not supported. 

 ods graphics on;
    
   proc gam data=equip;
       model removals=spline(month) / dist=Poisson method=gcv;
   run;

[StatDave]

The negative binomial distribution is supported in the newer PROC GAMPL and should generally be used rather than PROC GAM. Or, you can fit the model in PROC GLIMMIX by adding an EFFECT statement to define the spline you want.