function res = PSD(x) % MMA.m % Author: Alexander Khaustov; alexander dot khaustov at gmail dot com % Copyright (C) 2008 St.-Petersburg Institute of Cardiological Technics (Incart), www.incart.ru % This software is released under the terms of the GNU General % Public License (http://www.gnu.org/copyleft/gpl.html). % % A candidate for proper periodogram normalization len = length(x); f = fft(x); ac = real(ifft(f .* conj(f)/ len)) ; % autocorrelation xx = abs(fft(ac .* hamming(len))); %xx = abs(fft(ac)); res = xx(1:(len / 2 + 1)) / len; return;