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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/5_simulate_model.R
\name{simulate_model}
\alias{simulate_model}
\alias{simulate_model.default}
\title{Simulated draws from model coefficients}
\usage{
simulate_model(model, iterations = 1000, ...)
\method{simulate_model}{default}(model, iterations = 1000, component = "all", ...)
}
\arguments{
\item{model}{Statistical model (no Bayesian models).}
\item{iterations}{The number of draws to simulate/bootstrap.}
\item{...}{Arguments passed to \code{\link[insight:get_varcov]{insight::get_varcov()}}, e.g. to allow simulated
draws to be based on heteroscedasticity consistent variance covariance matrices.}
\item{component}{Should all parameters, parameters for the conditional model,
for the zero-inflation part of the model, or the dispersion model be returned?
Applies to models with zero-inflation and/or dispersion component. \code{component}
may be one of \code{"conditional"}, \code{"zi"}, \code{"zero-inflated"}, \code{"dispersion"} or
\code{"all"} (default). May be abbreviated.}
}
\value{
A data frame.
}
\description{
Simulate draws from a statistical model to return a data frame
of estimates.
}
\details{
\subsection{Technical Details}{
\code{simulate_model()} is a computationally faster alternative
to \code{bootstrap_model()}. Simulated draws for coefficients are based
on a multivariate normal distribution (\code{MASS::mvrnorm()}) with mean
\code{mu = coef(model)} and variance \code{Sigma = vcov(model)}.
}
\subsection{Models with Zero-Inflation Component}{
For models from packages \strong{glmmTMB}, \strong{pscl}, \strong{GLMMadaptive} and
\strong{countreg}, the \code{component} argument can be used to specify
which parameters should be simulated. For all other models, parameters
from the conditional component (fixed effects) are simulated. This may
include smooth terms, but not random effects.
}
}
\section{Model components}{
Possible values for the \code{component} argument depend on the model class.
Following are valid options:
\itemize{
\item \code{"all"}: returns all model components, applies to all models, but will only
have an effect for models with more than just the conditional model component.
\item \code{"conditional"}: only returns the conditional component, i.e. "fixed effects"
terms from the model. Will only have an effect for models with more than
just the conditional model component.
\item \code{"smooth_terms"}: returns smooth terms, only applies to GAMs (or similar
models that may contain smooth terms).
\item \code{"zero_inflated"} (or \code{"zi"}): returns the zero-inflation component.
\item \code{"dispersion"}: returns the dispersion model component. This is common
for models with zero-inflation or that can model the dispersion parameter.
\item \code{"instruments"}: for instrumental-variable or some fixed effects regression,
returns the instruments.
\item \code{"nonlinear"}: for non-linear models (like models of class \code{nlmerMod} or
\code{nls}), returns staring estimates for the nonlinear parameters.
\item \code{"correlation"}: for models with correlation-component, like \code{gls}, the
variables used to describe the correlation structure are returned.
}
\strong{Special models}
Some model classes also allow rather uncommon options. These are:
\itemize{
\item \strong{mhurdle}: \code{"infrequent_purchase"}, \code{"ip"}, and \code{"auxiliary"}
\item \strong{BGGM}: \code{"correlation"} and \code{"intercept"}
\item \strong{BFBayesFactor}, \strong{glmx}: \code{"extra"}
\item \strong{averaging}:\code{"conditional"} and \code{"full"}
\item \strong{mjoint}: \code{"survival"}
\item \strong{mfx}: \code{"precision"}, \code{"marginal"}
\item \strong{betareg}, \strong{DirichletRegModel}: \code{"precision"}
\item \strong{mvord}: \code{"thresholds"} and \code{"correlation"}
\item \strong{clm2}: \code{"scale"}
\item \strong{selection}: \code{"selection"}, \code{"outcome"}, and \code{"auxiliary"}
\item \strong{lavaan}: One or more of \code{"regression"}, \code{"correlation"}, \code{"loading"},
\code{"variance"}, \code{"defined"}, or \code{"mean"}. Can also be \code{"all"} to include
all components.
}
For models of class \code{brmsfit} (package \strong{brms}), even more options are
possible for the \code{component} argument, which are not all documented in detail
here.
}
\examples{
model <- lm(Sepal.Length ~ Species * Petal.Width + Petal.Length, data = iris)
head(simulate_model(model))
\donttest{
if (require("glmmTMB", quietly = TRUE)) {
model <- glmmTMB(
count ~ spp + mined + (1 | site),
ziformula = ~mined,
family = poisson(),
data = Salamanders
)
head(simulate_model(model))
head(simulate_model(model, component = "zero_inflated"))
}
}
}
\seealso{
\code{\link[=simulate_parameters]{simulate_parameters()}}, \code{\link[=bootstrap_model]{bootstrap_model()}}, \code{\link[=bootstrap_parameters]{bootstrap_parameters()}}
}
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