I am in the following situation: I already run my model in stan and got posterior sampling, but now I would like to compute other quantities like predictive distributions without resampling. For this purpose I created another stan model having as entries data covariates and posterior sampling and just a generated quantities block to compute what I need (through random-number generators).
Now my question: how should I properly run it in R? I tried calling stan command with fixed_parameters, but it is very slow and starts “sampling” (but what sampling? I do not have any parameters or model block!)