Perform approximate leave-one-out cross-validation based
on the posterior likelihood using the loo package.
For more details see `loo`

.

- x
A

`brmsfit`

object.- ...
More

`brmsfit`

objects or further arguments passed to the underlying post-processing functions. In particular, see`prepare_predictions`

for further supported arguments.- compare
A flag indicating if the information criteria of the models should be compared to each other via

`loo_compare`

.- resp
Optional names of response variables. If specified, predictions are performed only for the specified response variables.

- pointwise
A flag indicating whether to compute the full log-likelihood matrix at once or separately for each observation. The latter approach is usually considerably slower but requires much less working memory. Accordingly, if one runs into memory issues,

`pointwise = TRUE`

is the way to go.- moment_match
Logical; Indicate whether

`loo_moment_match`

should be applied on problematic observations. Defaults to`FALSE`

. For most models, moment matching will only work if you have set`save_pars = save_pars(all = TRUE)`

when fitting the model with`brm`

. See`loo_moment_match.brmsfit`

for more details.- reloo
Logical; Indicate whether

`reloo`

should be applied on problematic observations. Defaults to`FALSE`

.- k_threshold
The Pareto \(k\) threshold for which observations

`loo_moment_match`

or`reloo`

is applied if argument`moment_match`

or`reloo`

is`TRUE`

. Defaults to`0.7`

. See`pareto_k_ids`

for more details.- save_psis
Should the

`"psis"`

object created internally be saved in the returned object? For more details see`loo`

.- moment_match_args
Optional

`list`

of additional arguments passed to`loo_moment_match`

.- reloo_args
Optional

`list`

of additional arguments passed to`reloo`

.- model_names
If

`NULL`

(the default) will use model names derived from deparsing the call. Otherwise will use the passed values as model names.

If just one object is provided, an object of class `loo`

.
If multiple objects are provided, an object of class `loolist`

.

See `loo_compare`

for details on model comparisons.
For `brmsfit`

objects, `LOO`

is an alias of `loo`

.
Use method `add_criterion`

to store
information criteria in the fitted model object for later usage.

Vehtari, A., Gelman, A., & Gabry J. (2016). Practical Bayesian model evaluation using leave-one-out cross-validation and WAIC. In Statistics and Computing, doi:10.1007/s11222-016-9696-4. arXiv preprint arXiv:1507.04544.

Gelman, A., Hwang, J., & Vehtari, A. (2014). Understanding predictive information criteria for Bayesian models. Statistics and Computing, 24, 997-1016.

Watanabe, S. (2010). Asymptotic equivalence of Bayes cross validation and widely applicable information criterion in singular learning theory. The Journal of Machine Learning Research, 11, 3571-3594.

```
if (FALSE) {
# model with population-level effects only
fit1 <- brm(rating ~ treat + period + carry,
data = inhaler)
(loo1 <- loo(fit1))
# model with an additional varying intercept for subjects
fit2 <- brm(rating ~ treat + period + carry + (1|subject),
data = inhaler)
(loo2 <- loo(fit2))
# compare both models
loo_compare(loo1, loo2)
}
```