I came across a wonderful chapter on data fusion model using STAN.
The chapter describes two types of data fusion problems, and the authors provide some STAN codes. HOWEVER, they only provide the STAN code for the first type of classic data fusion problem.
May I ask someone here to provide some help on the STAN code for the second type, mixed levels of data aggregation? What I get stuck on is the part where there is a summation constraint for the missing (and imputed) variables. I do not know where in STAN for that summation constraint to appear.
Any help would be much appreciated! Thanks.