R/GR2.R

In highamm/sptotal: Predicting Totals and Weighted Sums from Spatial Data

#' Computes the Generalized R-squared.
#'
#' @param object is an object of class \code{slmfit}.
#' @return the value for generalized R-squared
#' @examples
#' data(exampledataset) ## load a toy data set
#' slmobj <- slmfit(formula = counts ~ pred1 + pred2, data = exampledataset,
#' xcoordcol = 'xcoords', ycoordcol = 'ycoords', areacol = 'areavar')
#' GR2(slmobj)
#' @export GR2


GR2 <- function(object) {


 if (!inherits(object, "slmfit")) return("Not a slmfit object")
  W <- object$DesignMat
  Vi <- object$FPBKpredobj$covmatsampi
  z <- object$Density
  betahat <- object$CoefficientEsts
  muhat <- sum(Vi %*% z) / sum(Vi)
  ones <- matrix(1, ncol = 1, nrow = length(z))
  gr2 <- 1 - t(z - W %*% betahat) %*% Vi %*% (z - W %*% betahat) /
    t(z - ones %*% muhat) %*% Vi %*% (z - ones %*% muhat)
  if (gr2 < 1e-8) {
    gr2 <- 0
  }
  as.vector(gr2)
}