The BYM2 model in stan_icar implements the model from: Morris et al "Bayesian hierarchical spatial models: Implementing the Besag York Mollié model in stan." They apply a normal prior to the logit-transformed 'mixing' parameter rho; geostan assigns a uniform prior to rho directly.
Use their method and test it out
Implement the model as done in the paper unless it seems worse than the current implementation
The BYM2 model in
stan_icar
implements the model from: Morris et al "Bayesian hierarchical spatial models: Implementing the Besag York Mollié model in stan." They apply a normal prior to the logit-transformed 'mixing' parameterrho
; geostan assigns a uniform prior torho
directly.