I’m running the brms package in R, and I’m trying to do an ordinal regression on the following data:

correct: proportion correct on a arithmetic task 0-1,

for example: 0.8421053, 0.8800000, 0.9130435, 0.9000000, 0.89285

performance_rating: 1-9,

for example: 5, 7, 6, 6, 6, 6, 3, 3, 3, 3, 8, 7, 4, 3, 3, 2, 6

condition: Control or Sleep Deprived.

This is my code.

```
fit_aritmetic_model_1 <- brm(
formula = performance_rating ~ 1 + correct + condition,
data = d_arithmetic,
family = cumulative("probit"),
control = list(adapt_delta = 0.99),
seed = 2023
)
```

The problem is that I’m getting a lot of these warnings:

```
Chain 1: Rejecting initial value:
Chain 1: Log probability evaluates to log(0), i.e. negative infinity.
Chain 1: Stan can't start sampling from this initial value.
```

After a couple of iterations, it finds values that work, and it seems to run well (but I’m no expert, so maybe I shouldn’t trust the results). Nevertheless, I want to learn how to avoid this problem.

How do I adjust my code to get rid of it?