list_fixed_effects {mixedbiastest}R Documentation

List Fixed Effects from an lmerMod Object

Description

This function lists the fixed effects coefficients from an 'lmerMod' object, providing the index and name of each coefficient. This can help users construct contrast vectors ('k_list') for use with the 'mixedbiastest' function.

Usage

list_fixed_effects(model)

Arguments

model

An object of class 'lmerMod' fitted using 'lmer' from the 'lme4' package.

Value

A data frame with two columns:

Index

The index of each fixed effect coefficient.

Coefficient

The name of each fixed effect coefficient.

Acknowledgments

Development of this package was assisted by GPT o1-preview, which helped in constructing the structure of much of the code and the roxygen documentation. The code is based on the R code provided by Karl and Zimmerman (2020).

Examples

if (requireNamespace("plm", quietly = TRUE) && requireNamespace("lme4", quietly = TRUE)) {
  library(lme4)
  data("Gasoline", package = "plm")
  # Fit a random effects model using lme4
  mixed_model <- lmer(lgaspcar ~ lincomep + lrpmg + lcarpcap + (1 | country),
                      data = Gasoline, REML = FALSE)

  # List fixed effects
  fixed_effects <- list_fixed_effects(mixed_model)
  print(fixed_effects)

  # Suppose we want to test the contrast: lincomep - lcarpcap
  p <- nrow(fixed_effects)
  k <- rep(0, p)
  k[fixed_effects$Index[fixed_effects$Coefficient == "lincomep"]] <- 1
  k[fixed_effects$Index[fixed_effects$Coefficient == "lcarpcap"]] <- -1

  # Run the bias test with the custom contrast
  result <- mixedbiastest(mixed_model, k_list = list(k))
  print(result)
  plot(result)
} else {
  message("Please install 'plm' and 'lme4' packages to run this example.")
}

[Package mixedbiastest version 0.3.0 Index]