function [b,Pxx]=pppp(b);

[time,x]=pmod(b,0.65,2048);
b=b;
y=diff(x);
X=fft(y,2048);
Pxx=X.*conj(X)/2048;
% Power spectrum can be parametrized.

plot(Pxx,'b');grid;
xlabel('Frequencies');
ylabel('Reduced scale');
axis([1 2048 0 0.0003]);
title(['Power spectrum for \alpha=', num2str(b)])

% "Complex and Chaotic Nonlinear Dynamics. 
% Advances in Economics and Finance, 
% Mathematics and Statistics" 
% T.Vialar, Springer 2009.
% Copyright(c).