R: Posterior Predictive Checks for 'brmsfit' Objects

pp_check.brmsfit {brms} | R Documentation

## Posterior Predictive Checks for `brmsfit` Objects

### Description

Perform posterior predictive checks with the help of the bayesplot package.

### Usage

    ## S3 method for class 'brmsfit'
    pp_check(
      object,
      type,
      ndraws = NULL,
      nsamples = NULL,
      group = NULL,
      x = NULL,
      newdata = NULL,
      resp = NULL,
      draw_ids = NULL,
      subset = NULL,
      ...
    )

### Arguments

`object` | An object of class `brmsfit`.
`type` | Type of the ppc plot as given by a character string. See `PPC` for an overview of currently supported types. You may also use an invalid type (e.g. `type = "xyz"`) to get a list of supported types in the resulting error message.
`ndraws` | Positive integer indicating how many posterior draws should be used. If `NULL` all draws are used. If not specified, the number of posterior draws is chosen automatically. Ignored if `draw_ids` is not `NULL`.
`nsamples` | Deprecated alias of `ndraws`.
`group` | Optional name of a factor variable in the model by which to stratify the ppc plot. This argument is required for ppc `*_grouped` types and ignored otherwise.
`x` | Optional name of a variable in the model. Only used for ppc types having an `x` argument and ignored otherwise.
`newdata` | An optional data.frame for which to evaluate predictions. If `NULL` (default), the original data of the model is used. `NA` values within factors are interpreted as if all dummy variables of this factor are zero. This allows, for instance, to make predictions of the grand mean when using sum coding.
`resp` | Optional names of response variables. If specified, predictions are performed only for the specified response variables.
`draw_ids` | An integer vector specifying the posterior draws to be used. If `NULL` (the default), all draws are used.
`subset` | Deprecated alias of `draw_ids`.
`...` | Further arguments passed to `predict.brmsfit` as well as to the PPC function specified in `type`.

### Details

For a detailed explanation of each of the ppc functions, see the `PPC` documentation of the bayesplot package.

### Value

A ggplot object that can be further customized using the ggplot2 package.

### Examples

    ## Not run:
    fit <-  brm(count ~ zAge + zBase * Trt
                + (1|patient) + (1|obs),
                data = epilepsy, family = poisson())

    pp_check(fit)  # shows dens_overlay plot by default
    pp_check(fit, type = "error_hist", ndraws = 11)
    pp_check(fit, type = "scatter_avg", ndraws = 100)
    pp_check(fit, type = "stat_2d")
    pp_check(fit, type = "rootogram")
    pp_check(fit, type = "loo_pit")

    ## get an overview of all valid types
    pp_check(fit, type = "xyz")

    ## End(Not run)

[Package brms version 2.16.1 Index]