If I try using `stan_polr`

with random effects:

```
bayes <- stan_polr(
value ~ 1 | q,
long_table,
prior = R2(.5, what="mean"),
chains=parallel::detectCores()
)
```

I get an error:

```
Error in dimnames(x) <- dn :
length of 'dimnames' [2] not equal to array extent
In addition: Warning message:
In Ops.factor(1, q) : ‘|’ not meaningful for factors
```

I’m not sure what the warning means; to me, it seems that the idea of a is perfectly well-defined. To be fair, I’m not all that used to rstanarm’s syntax, so I might be misunderstanding it.

I’m trying to do an IRT-like model where outcomes are ordinal and each question has a different difficulty, and I’d like to partially pool the difficulties together to get better estimates.