R/getFE.R

In vjilmari/vjihelpers: Toolbox of typical helper functions I need

#' Fixed effects from linear mixed model
#'
#' @param model Fitted model with lmerTest.
#' @param ci.level Width of confidence intervals.
#' @param round Rounding for all but p-values (default 2).
#' @param p.round Rounding for p-values (default 3).
#'
#' @return A formatted data frame of fixed effects.
#' @export
#'
#' @examples
#' set.seed(234)
#' n1 <- 3 # groups
#' n2 <- 3 # observations per groups
#'
#' dat <- data.frame(
#'   group = rep(c(LETTERS[1:n1]), each = n2),
#'   x1 = sample(1:5, n1 * n2, replace = TRUE),
#'   x2 = sample(1:5, n1 * n2, replace = TRUE),
#'   x3 = sample(1:5, n1 * n2, replace = TRUE)
#' )
#' getFE(lmerTest::lmer(x1 ~ x2 + x3 + (1 | group), data = dat, REML = FALSE))
getFE <- function(model, ci.level = .95, round = 2, p.round = 3) {
  p.cut <- 1 - ((1 - ci.level) / 2)

  coefs <- data.frame(summary(model)$coefficients)
  coefs$lower <- coefs[, 1] - stats::qt(p = p.cut, df = coefs[, "df"]) * coefs[, 2]
  coefs$upper <- coefs[, 1] + stats::qt(p = p.cut, df = coefs[, "df"]) * coefs[, 2]
  coefs <- cbind.data.frame(round(coefs[, 1:4], round),
    p = round(coefs[, 5], p.round),
    LL = round(coefs$lower, round),
    UL = round(coefs$upper, round)
  )
  colnames(coefs) <-
    c("Est.", "SE", "df", "t", "p", "LL", "UL")

  return(coefs)
}