copy/move `rhat()` and `neff_ratio()` to rstan(arm)?

[strengejacke]

I was looking for functions to extract rhat and the ratio for number of effective samples, and found those in the brms-package for brmsfit-objects, but not in rstan or rstanarm for stanreg-objects (where I would expect those functions to be).

Instead, I later realized that these are in the bayesplot-pkg. Wouldn't it make more sense to have the functions (also) in rstan/rstanarm as well?

[tjmahr]

@jgabry would the generics go in rstantools and the S3 methods go into rstan and rstanarm? I'm not sure about the stanverse organization in this regard.

[jgabry]

Circling back through old issues. Yes I think having these as rstantools generics makes the most sense. I’ll open an issue for it over there.

_{Sent with GitHawk}

[jgabry]

https://github.com/stan-dev/rstantools/issues/31

_{Sent with GitHawk}

[avehtari]

I think these are now in posterior. Maybe this issue can be closed?

[strengejacke]

Yes, I think so, too.