I am not an expert on the formula syntax for specifying models. I understand that it is always assumed that there is an intercept so that y ~ 1 + x would be equivalent to y ~ x.

I think this is the case, regardless of varying intercepts/slopes. So y ~ 1 + x + (1|g) would be the same as y ~ x + (1|g). I have, however, seen that the different syntax has a big effect on the time it takes for the model to run. The posterior summaries are the same, but the former’s chains take longer to finish.

Hi @fazepher, that’s definitely not expected. Like @ssp3nc3r was getting at with his example, there shouldn’t be a difference other than variation from things like the quality of random initial values.

Can you share an example where you see this behavior? That would be really interesting if I could reproduce it.