nb <- NbClust(d, distance = "euclidean", min.nc = 2, max.nc = 30, method = "complete", index ="all")

set.seed(123)
         d <- data.frame(x = unlist(lapply(1:500, function(i) rnorm(100, runif(1)*2^2))),
               y = unlist(lapply(1:500, function(i) rnorm(100, runif(1)*2^2))),
               z = unlist(lapply(1:500, function(i) rnorm(100, runif(1)*2^2))))