clear
clc

x=[101,82,66,35,31,7,20,92,154,125,85,68,38,23,10,24,83,132,131,118,90,67,60,47,41,21,16,6,4,7,14,34,45,43,48,42,28,10,8,2,0,1,5,12,14,35,46,41,30,24,16,7,4,2,8,17,36,50,62,67,71,48,28,8,13,57,122,138,103,86,63,37,24,11,15,40,62,98,124,96,66,64,54,39,21,7,4,23,55,94,96,77,59,44,47,30,16,7,37,74];
N=length(x);
L=2;
M=length(x)/L;
xx=zeros(L,M);
I=zeros(L,512);
P=zeros(1,N);
n=0:M-1;
for(i=1:L)
    xx(i,:)=x((i-1)*M+1:i*M);
end
W=bartlett(M);
U=mean(W.^2);
w=[0:512-1]*2*pi/512;
for(i=1:L)
    y=xx(i,:).*W';
    Y=fft(y,512);
    I(i,:)=(Y.^2)/(M*U);
end
P=abs(sum(I)./L);
%P=10*log(P);
N0=ceil(length(P)/2);
P=P(1:N0);
plot(w(1:N0),P);grid on;title('改進周期圖法功率譜(Bartlett Window)');xlabel('w');ylabel('P(w)');axis([0,pi,0,2*10^4]);