#' Spatially correlated variance (SCV)
#'
#' @description
#' Compute the proportion of the variance that is spatially correlated.
#'
#' @param obj Variogram model fitted with available function in geostatistical packages such as
#' __gstat__, __geoR__, and __georob__.
#'
#' @param digits Integer indicating the number of decimal places to be used.
#'
#' @return
#' Numeric value indicating the proportion of the variance that is spatially correlated.
#'
#' @author Alessandro Samuel-Rosa \email{alessandrosamuelrosa@@gmail.com}
#'
#' @seealso [pedometrics::variogramBins()]
#'
#' @aliases vgmSCV vgmSCV.variomodel vgmSCV.variogramModel vgmSCV.georob
#'
#' @concept variogram
#' @examples
#' if (all(c(require(gstat), require(sp)))) {
#' library(gstat)
#' library(sp)
#' data(meuse)
#' sp::coordinates(meuse) <- ~ x + y
#' vgm1 <- gstat::variogram(log(zinc) ~ 1, meuse)
#' fit <- gstat::fit.variogram(vgm1, gstat::vgm(1, "Sph", 300, 1))
#' res <- vgmSCV(fit)
#' }
# FUNCTION - general ###############################################################################
#' @export
vgmSCV <-
function(obj, digits = 4) {
UseMethod("vgmSCV")
}
# FUNCTION - geoR ##################################################################################
#' @rdname vgmSCV
#' @export
vgmSCV.variomodel <-
function(obj, digits = 4) {
res <- obj$sigmasq / (obj$sigmasq + obj$tausq)
res <- round(unname(res), digits = digits)
return(res)
}
# FUNCTION - gstat #################################################################################
#' @export
#' @rdname vgmSCV
vgmSCV.variogramModel <-
function(obj, digits = 4) {
res <- obj$psill[2] / sum(obj$psill)
res <- round(unname(res), digits = digits)
return(res)
}
# FUNCTION - georob ################################################################################
#' @export
#' @rdname vgmSCV
vgmSCV.georob <-
function(obj, digits = 4) {
res <- obj$param[1] / sum(obj$param[1:3])
res <- round(unname(res), digits = digits)
return(res)
}
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