#Function to determine the periodogram of a set of data. #Written by Bob Sherman, Walter Willinger per <- function (z) {n<-length(z) (Mod(fft(z))^2/(2*pi*n)) [1:(n %/% 2 + 1)]} #Function to determine the periodogram of a set of data for stable process. #Writen by Vadim Teverovsky perstable <- function (z) {n<-length(z) norm_sum((z^2)[1:n]) (Mod(fft(z))^2/(2*pi*n*norm)) [1:(n %/% 2 + 1)]}