R/gini.R

In tibo31/GeoXp: Interactive Exploratory Spatial Data Analysis

gini <- function (var) {
  
  n <- length(var)
  vsort <- sort(var)

  Xk <- vsort

  f <- rep(1,length(Xk))
  f <- f/n

  F <- rep(0,length(Xk),1)

  for (i in 1:length(Xk))
    F[i] <- length(which(var <= Xk[i]))

  F <- F/n

  g <- (Xk*f)/(sum(var)/n)
  G <- cumsum(g)

  F1 <- matrix(rep(t(f), length(f)), ncol = dim(t(f))[2], byrow = FALSE)
  F2 <- matrix(rep(t(f), length(f)), ncol = dim(t(f))[2], byrow = TRUE)
  X1 <- matrix(rep(t(Xk), length(Xk)), ncol = dim(t(Xk))[2], byrow = FALSE)
  X2 <- matrix(rep(t(Xk), length(Xk)), ncol = dim(t(Xk))[2], byrow = TRUE)

  T <- (F1*F2)*abs(X1-X2)
  gini <- sum(T)/(2*sum(var)/n)

  F <- c(0, F)
  G <- c(0, G)

return(list(f = f, F = F, g = g, G = G, gini = gini))
}