This function returns the effective sample size (ESS).

## Usage

```
effective_sample(model, ...)
# S3 method for class 'brmsfit'
effective_sample(
model,
effects = c("fixed", "random", "all"),
component = c("conditional", "zi", "zero_inflated", "all"),
parameters = NULL,
...
)
# S3 method for class 'stanreg'
effective_sample(
model,
effects = c("fixed", "random", "all"),
component = c("location", "all", "conditional", "smooth_terms", "sigma",
"distributional", "auxiliary"),
parameters = NULL,
...
)
```

## Arguments

- model
A

`stanreg`

,`stanfit`

,`brmsfit`

,`blavaan`

, or`MCMCglmm`

object.- ...
Currently not used.

- effects
Should results for fixed effects, random effects or both be returned? Only applies to mixed models. May be abbreviated.

- component
Should results for all parameters, parameters for the conditional model or the zero-inflated part of the model be returned? May be abbreviated. Only applies to brms-models.

- parameters
Regular expression pattern that describes the parameters that should be returned. Meta-parameters (like

`lp__`

or`prior_`

) are filtered by default, so only parameters that typically appear in the`summary()`

are returned. Use`parameters`

to select specific parameters for the output.

## Details

**Effective Sample (ESS)** should be as large as possible, altough
for most applications, an effective sample size greater than 1,000 is
sufficient for stable estimates (Bürkner, 2017). The ESS corresponds to the
number of independent samples with the same estimation power as the N
autocorrelated samples. It is is a measure of “how much independent
information there is in autocorrelated chains” (*Kruschke 2015, p182-3*).

## References

Kruschke, J. (2014). Doing Bayesian data analysis: A tutorial with R, JAGS, and Stan. Academic Press.

Bürkner, P. C. (2017). brms: An R package for Bayesian multilevel models using Stan. Journal of Statistical Software, 80(1), 1-28

## Examples

```
# \donttest{
library(rstanarm)
model <- suppressWarnings(
stan_glm(mpg ~ wt + gear, data = mtcars, chains = 2, iter = 200, refresh = 0)
)
effective_sample(model)
#> Parameter ESS
#> 1 (Intercept) 172
#> 2 wt 181
#> 3 gear 175
# }
```