Z-residuals for Poisson models fitted with brms

Zresidual.poisson.brms() is the S3 method for Zresidual() when applied to Poisson models fitted with brms::brm() and family = poisson(). Objects are dispatched here when the fitted object is a "brmsfit" with brms::family(object)$family == "poisson" and has been internally tagged with the class "poisson.brms" by Zresidual().

In normal use, users should call Zresidual() directly on the brmsfit object (for example Zresidual(fit)), rather than calling Zresidual.poisson.brms() explicitly.

Usage

# S3 method for class 'poisson.brms'
Zresidual(object, nrep = 1, data, type, method = "iscv", ...)

Arguments

object

A brmsfit object with Poisson family (brms::family(object)$family == "poisson").

nrep

Integer; the number of replicated Z-residual sets to generate. Default is 1.

data

Optional data frame used for prediction or residual computation. If NULL (default), the data stored inside the brmsfit object are used.

type

Optional character string controlling the residual type, interpreted by the underlying implementation (if used).

method

Character string specifying the residual calculation method: "iscv" for importance-sampled cross-validated randomized predictive p-values, "rpost" for posterior predictive p-values, or "mpost" for marginal posterior predictive p-values. Default is "iscv".

...

Further arguments passed from Zresidual(). They are ignored by this method but are accepted for consistency with the generic.

Value

A numeric matrix of Z-residuals (one column per replication) as returned by Zresidual_poisson_brms(), with the class "zresid" added to its class vector.

Examples

if (FALSE) { # \dontrun{
  library(brms)
  fit_pois <- brm(y ~ x1 + x2, data = df,
                  family = poisson())

  ## ISCV-based Z-residuals
  z_pois <- Zresidual(fit_pois, method = "iscv")

  ## Posterior predictive Z-residuals with 2 replicates
  z_pois_post <- Zresidual(fit_pois, method = "rpost", nrep = 2)
} # }