Variable importance for Mixed Models

calc.relip.mm.R

calc.relip.mm <- function(model,type='lmg') {
  if (!isLMM(model) & !isGLMM(model)) {
    stop('Currently supports only lmer/glmer objects', call. = FALSE)
  }
  require(lme4)
  X <- getME(model,'X')
  X <- X[,-1]
  Y <- getME(model,'y')
  s_resid <- sigma(model)
  s_effect <- getME(model,'theta')*s_resid
  s2 <- sum(s_resid^2,s_effect^2)
  V <- Diagonal(x = s2,n=nrow(X))
  YX <- cbind(Y,X)
  cov_XY <- solve( t(YX) %*% solve(V) %*% as.matrix(YX))
  colnames(cov_XY) <- rownames(cov_XY) <- colnames(YX)
  importances <- calc.relimp(as.matrix(cov_XY),rela=T,type=type)
  return(importances)
}