I have this model:

```
brm(bf(Y ~ intercept + x * slope * setting,
intercept ~ 1 + (1|id_f),
slope ~ 1 + (1|id_f),
setting ~ setting_c,
nl = TRUE))
```

`setting_c`

is a factor with 4 levels.

I want the first level to have an effect of 1 (no effect when it is multiplied with `slope`

), and the remaining 3 levels to be estimated.

Is it possible to specify this?

(Also, is it possible to specify this model as a linear model?)