insert etiology regression for latent status code chunk into .bug file
insert_bugfile_chunk_reg_etiology(Eti_formula, Jcause, ppd = NULL)a long character string to be inserted into .bug model file as distribution specification for latent status
Etiology regression formula; Check model_options$likelihood$Eti_formula.
The number of distinct causes, i.e., categories of latent health
status; equals length(model_options$likelihood$cause_list).
Default is NULL; set to TRUE for posterior predictive checking