When running the Bayesian conditional logistic regression model using stan_clogit, I always got this error message (see below). But it seems that the analysis still went quite well. I don’t understand this error, but it seems that it does not influence the calculation.

Warning in model.matrix.default(mt, mf, contrasts) :

non-list contrasts argument ignored

Using the dataset ‘infert’ as an example, the code used is as below:

```
library(rstanarm)
post <- stan_clogit(case ~ spontaneous + induced,
data = infert[order(infert$stratum), ], # order necessary
strata = stratum, QR = TRUE,
cores = 2, seed = 12345)
summary(post)
```